OCR Text |
Show 90 ZOOLOGICAL COLLECTIONS M A D E DURING [Jan. 4, nearly vertically; below the ambitus and approaching the actinostome the rows become considerably flattened out and take on a more horizontal direction. Test not thick, very nearly circular, a good deal flattened; spines rather long, greenish, with (when dry) a reddish purplish tip ; in each area there are two rows of primary tubercles, of" which the interambulacral are considerably the larger; in both sets the diminution in size on the actinal surface is very vapid and very marked ; a row of small tubercles, separating the two rows of primary tubercles, extends from the actinostome to some way above the ambitus, in the ambulacral area; there are but few secondary tubercles, on each coronal plate ; and as the plates are high, there is no appearance of crowding. The poriferous zones are of a greenish-grey colour, and the two inner or upper pairs of pores are placed at a little distance from the outer or lower six pairs of pores; the spaces between the primary tubercles of the ambulacral area are of a reddish colour. The actinostome is moderately large ; but there are no deep cuts, and no large plates developed on the buccal membrane. As in S. bullatus, the ridge connecting the auricles is exceedingly low; the abactinal system is comparatively small, the number of anal plates not small; the madreporic is not much larger than the genital plates. As in S. bullatus, none of the ocular plates reaches the anal area. I cannot say whether the presence of short white spinous tubercles rising up so as to form a kind of anal tube is an individual peculiarity of the specimen under description. The following are the more important measurements: - Diameter of Diameter Height actino- abactinal anal Ambul. Interamb. Length of test, of test, stome. system, system, area. area. of spine. 39 21 13 8"5 5 9 115 22 One specimen. Tom Bay, 0-30 fms. ; bottom, sand, kelp, and mud. ECHINUS MAGELLANICUS (Philippi). E. magellanicus, Philippi, Archiv fur Naturg. xxiii. p. 130 (1857). Two species of the genus Echinus have been recorded from the Straits of' Magellan, E. magellanicus and E. margaritaceus. Without entering into any general discussion of their peculiarities, it will be sufficient to point out (in consequence of the somewhat contradictory statements that have been put out regarding them) that E. magellanicus can be readily distinguished by its larger number of primary tubercles. No specimens of E. margaritaceus were obtained in this collection. Those of E. magellanicus are all small in size. They were taken at:- (1) Tom Bav. (2) Cockle Cove. (3) Trinidad Channel. |