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 di- 

 stinguishable : — the articular portions of the occipital bone (6), 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 (Scheitelschliifenbeine) (c'), which are 

 broad and arched, forming laterally the roof of the vestibule. The 

 frontal bones (c). The long and bent quadrate bones (re). The 

 pterygoid bones (m), with their teeth- Between them the great opening 

 for the fifth pair (#)•" " The nasal bones are wanting. The maxillae 

 (£) and the praemaxillae (/)." A fair figure (tab. vii. fig. 2) accom- 

 panies 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 os- 

 sification of the epiotic bears the number appropriated to the " mas- 

 toid" by Professor Owen. Fischer (' Anatomische Abhandlungen 

 fiber die Perennibranchiaten und Derotremen,' 18G4) 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 con- 

 tained 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 pteryyoi- 

 deum (pterygopalatine), the os petrosum (epiotic and opisthotic), the 

 os parietali-frontale (parietal), the osfrontale anterius (frontal), the 

 os frontale posterius (prootic), the vomers, the os tympanicum (squa- 

 mosal), and the osjuyale (quadrato-jugal) ; in the mandible, the os 

 dentate (dentary), and the os anyulare (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 XXX. 



* Stanniua observes ('Handbuch. Die Amphibien,'p.38), "Bei den Proteidea 

 [Proteus and Menobranchus] sind die niedrigen Seitenwiinde der beiden vorder- 



13* 



