us 



Class REPTILIA. 

 Order BATRACHIA. 



Genus Sirm. 



576. One of the anterior vertcbrse of the Siren (Siren lacrrtina), which supports 

 short plcurapophyscs or costal appendages. 



The whole vertebra is remarkable for iu itnmgly ridged exterior : the body presents a 

 deep conical excavation at each end : the neural (pine form* a strong ridge above the arch, 

 and bifurcates posteriorly to terminate upon the posterior lygapophries. A strong hrpapo- 

 physial ridge U left, by defect of ossification on each side, to form the under surface of ihr 

 centrum. A parapophysial ridge extends from a short anterior parapnphrsis to the longer 

 parapophysial part of the transverse process at the posterior part of the vertebra. A dimjx>- 

 phyiial ridge extends above and nearly parallel with the former, from the anterior zygapo- 

 physis to the diapophysial |>rt of the transverse process. A third short ridge is continued 

 from the former to the posterior tygapophysu. The vacuities between these several ridgn 

 resemble those which are common in the incompletely ossified vertebra of fishes. 



Ilunterian. 

 576 a. The skull and four following vertebrae of the Sire* lacfrlina. 



The cranial cavity has been laid open, and the large otolite and vestibular sac are exposed 

 in the right otocrane. The body of the atlas articulates by two almost flat vertical articular 

 surfaces to two similar condylrs from the cxoccipitals. A continuous broad flat expanse of 

 bone represents the bodies of the cranial segments. 



The confluent pamccipital and mastoid project backwards as a broad compressed plate, from 

 the upper part of which a mastoid ridge extends forwards along the side of the cranium, and 

 gives attachment to the tympanic, which arches forwards and downwards, increasing in thick- 

 new and forming a three-sided cone, the base of which forms the articular cavity for the 

 broad convex ooodyle of the lower jaw : both the frontal and nasal bones are divided by a 

 median suture. The premaxillaries consist of a short, transverse, trenchant, alveolar plate, 

 and a long and slender nasal part, the point of which is wedged between the nasal and frontal. 

 The prefronud, notched by the olfactory nerve, extends from the frontal, which overarches it, 

 to the vomer and palatine below. The palatine is beset with eight short oblique raws of den- 

 ticles, and four similar rows extend backwards on short pterygoids. 



The lower jaw consists of articular, angular, splenial and dentary piece*. The angular and 

 splenial seem to be confluent. There is no coronoid process. The horny, trenchant covering 

 of the alveolar plate of the maxillary terminates behind in an angular elevation of that mar- 



