| OCR Text |
Show 22 CRUSTACEA. seas. With the exception of the Orithyire, we observe but five distinctly marked segments in the tail of the males, while that of the females presents seven. '\i\Te will begin with those in which all the feet, except the claws, are natatory. MATUTA, Fabr. _The Matutre have an almost orbicular shell a1·med on each side With a very stout tooth in the form of a spine; the superior edge of the hands dentated like a crest, and their external fuce studded w~th pointed tubercles; the third joint of the external foot-jaws, ~v1thout any appa1·ent emargination, te1·minates in a point, so that . 1t forms, with the p1·eceding joint, an elongated and almost rightang~ ed tria_ngle. The external antennre are very small, and the ocular pe<hcles shghtly arcuated. De Geer men~ions a species-Cancer latipes, which he says is fro"_l the American seas, and has its front terminated hy a straight and entire margin. All those we have seen, however(!), were brought from the East, and the middle of that ~::gm always p1·esents a bidcntated or emarginated projection. PoLYBIUs, Leach, Is allied to the Portuni, but the shell is proportionably narrower and more rounded; the sides are merely furnished with r . te.e th . Th. e th'I r d .. t f on maly JOin o the external foot-jaws is obtuse and emar-gmated. fhe eyes are much thicker than their pedicles and glo-bular. ' But a single sp~cies is as yet known(2); it was found on the c~ast of Devonshire, and has also been observed by M. D'Or· hJgny on the sea-coast of the western departments of France(3) In all the followi g · · f . n swimmers, the two posterior feet only are ormed hke fins(4). We may first separate those whose shell is almost ovoid and trans· ( 1) M. victor, Fab.; Herbst VI 44 M. l . lunaria Leach zo 1 M' 11 '' ' .:--:, · P antpes, Fub.; Herbst., x1viii, 6; M. ' ' 0 • ISCe ., CXXVII, .J-5, var. ·-JJf. p • • b l-2. Perhaps we should refer the fl . . ' . eronn, J ., t::~.b., cad., d' /l( . t H' osstl spectes culled by .M. Desmarest Portune (2e)r tcPaorl ' b · tst1. !1N. at.1 -d--e-~s· Crust :Foss V 5 h' ' ., • ' ' tot ts genus, or the Munsu, Leach. y ws enswwn, Leach, Ma.l::tc. IJrit. IX B (3) The tarsi of the intermediate feet of th: Po\ . . pressed into a fin· they · ht b 1 · r umnt, Leach, are almost com- ' mtg e P aced after the Polybii ( 4) Always wider and more oval than the preceding tar~i. DECAPODA. 23 versely truncated before, and where the tail of the males (the only sex known) consists of seven distinct segments. Such is the 0RYTHYIA, Fabr. The only species known,-Orith. mamillaris, Fabr., Cancer bimaculatus, Herbst., X VIII, 101, is found in the sea of China, Ol' at least forms a part of the collections of Insects sold by its inhabitants to foreigners. The ocular pedicles are longer in proportion than those of the Portuni. The shell of the last swimmers is much wider before than behind,. forming either the segment of a circle narrowed towards the tail and truncated, or a trapezium, or is almost in the shape of a hea~t. Its greatest transverse diameter generally surpasses the opposite one. There are but five segments in the tail of the males, instead of the seven found in that of the females, the number usually peculiar to the tail of the Decapoda; the third and the two following ones are confounded or form but one; frequently, however, traces of them are discove1·ed, at least on the sides. We will first separate those whose eyes are supported by very long and slender pedicles, arising from the middle of the anterior margin of the shell, extending to its lateral angles, and received into a groove run under the edge. Such is the PonoPHTIIALMus, Lam., Where the shell forms a transverse trapezium, wider and straight before with a long spiniform tooth behind the ocular cavities. The claws are elongated, spiny, and similar to those of most of the ~pe-cies of the genus Lupa, Leach. The only living species known(l) inhabits the coasts of the Isle of France and those of the neighbouring seas. The valuable cabinet of one of the most learned fossil conchylidogisls of Eu1·ope, contains an' internal cast of a fossil Podophthalmus, to which M. Desmarest has affixed the name of its possessor, M. de France(2). The ocular pedicles of the other Crustacea, belonging to this sec-tion, are short, occupy but a very small portion of the transverse diameter of the shell, are placed in oval cavities, and resemble. generally, those of the ordinary Crabs with which these swimmers (1) PodoplLthalmus spinosus, Latr., Gener. Crust. et Insect., I, 1, and II, 1; . Leach, Zoot., Miscell. cxlviii; Portunus vigil, Fub. (2) Hist. Nat. des Crust. Foss., V, 6, 7, 8. |
