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Show 1874.J PROF. T. H. HUXLEY ON MENOBRANCHUS. 187 forwards and downwards." " As in Menopoma, the rami of the mandible are not ankylosed together, though the three pieces of each ramus are more closely united than in Menopoma. In the skull are distinguishable :-- the articular portions of the occipital bone (b), which, below, appear not to be separate from the sphenoid (Keilbein) and vomer; above, however, they do not extend to the top of the skull. The parieto-temporal bones (Scheitelschlafenbeine) (c1), which are broad and arched, forming laterally the roof of the vestibule. The frontal bones (c). The long and bent quadrate bones (n). The pterygoid bones (m), with their teeth. Between them the great opening for the fifth pair (x)." " The nasal bones are wanting. The maxillae (k) and the praemaxillee (/)." A fair figure (tab. vii. fig. 2) accompanies this short notice, from which it is clear that Mayer's "maxillae" are the vomers, and his "quadrate" the squamosal. A short description of a skull of Menobranchus in the Museum of the Royal College of Surgeons is to be found in the first volume of the 'Catalogue of the Osteological Series,' p. 116. The prominent ossification of the epiotic bears the number appropriated to the " mastoid" by Professor Owen. Fischer ('Anatomische Abhandlungen iiber die Perennibranchiaten und Derotremen,' 1864) has given an excellent description and figure of the hyoidean and branchial arches of Menobranchus. The fullest account, and the best figure, of the skull of Menobranchus which I have met with, however, are contained in Van der Hoeven's 'Ontleed- en Dierkundige Bijdragen tot de Kennis van Menobranchus' published in 1867. Van der Hoeven distinguishes the following bones:-the lateral occipitals (exocci-pitals mihi), the os sphenoideum (parasphenoid), the os pterygoi-deum (pterygopalatine), the os petrosum (epiotic and opisthotic), the os parietali-frontale (parietal), the os frontale anterius (frontal), the os frontale posterius (prootic), the vomers, the os tympanicum (squamosal), and the os jugate (quadrato-jugal); in the mandible, the os dentate (dentary), and the os angulare (splenial). In his description of the hyoidean and branchial arches, Van der Hoeven agrees with Fischer. As to the manner in which the hyoid is connected with the suspensorium, the latter writer observes that the ascending branch of the hyoidean cornu is connected by ligament with the posterior surface of the "os tympanicum." " In Hypochthon a second strong ligament extends from the dorsal apex of the hyoidean cornu to the lower jaw. In none of the other genera [of Perenni-branchiata and Derotremata] have I observed this second attachment to the lower jaw. A tendon, which, in Menobranchus, runs external to the posterior point of the hyoidean cornu, parallel with the latter, downwards and forwards, belongs to the second portion of the digastric muscle." Nevertheless it will be seen that this second ligament exists no less in Menobranchus than in Proteus. It is also to be found in Siren and Siredon. None of the authors cited mentions the cartilaginous framework of the skull *. The cranium of Menobranchus viewed from above (Plate X X X . * Stannius observes('Handbuch. Die Amphibien,'p. 38), "Bei denProteidea \Proteus and Menobranchus'] sind die niedrigen Seitenwiinde der beiden vorder- 13* |
