174 



EEPTILIA 



CLASS III 



foramen. The orbits are oval, relatively small, and placed sliglitly in front of tlie 

 middle ; not far removed from them are the external nares. The unpaired frontal is 

 much elongated, the premaxillae only moderately so, and the prefrontals are small and 

 triangnlar, The long and narrow maxillae nnite posteriorly with a slender jugal, 



FiG 270. 



Nothosaurus imrahüis, Münst. Muschelkalk ; Bayreuth, Germany. A, The five anterior cervicals. 

 B, Tvvo dorsals. C, Three caudal vertebrae, 1/2 (after von Meyer). 



which entei-s into the temporal arcade. Pterygoids and palatines are strongly 

 developed ; the internal nares are placed far forwards, on either side of the paired 

 vomer. A Single series of conical, slightly curved, and striated teeth (Fig. 272) is 



borne by the maxillae, pre- 

 maxillae, and dentary. All of 

 the rostral and one or two of 

 the anterior maxillary teeth are 

 considerably enlarged. 



O'sving to the sutural union 

 between the vertebral centra and 

 their neural arches, the former 

 are usnally found detached in 

 the fossil State, and exhibit a 

 crnciform Impression on the 

 dorsal surface (Fig. 275). There 

 are about twenty cervicals (Fig. 

 276), all of which excepting atlas 

 and axis bear short, curved, 

 double-headed ribs. The ribs of 

 the trank region are stout, single- 

 headed, and attached to the trans- 

 verse processes of the neural 

 arches. In tliis region the 

 neural spines are more strongly 

 developed, and the zygapophyses 

 more weakly, than elsewhere in 

 the vertebral column. The caudal vertebrae have single-headed ribs attached to their 

 centra, and also small chevron bones. The abdominal ribs comprise a median longi- 

 tudinal series sharply bent in the middle line, and a paired lateral series. 



In the pectoral arch (Fig. 277) the cla vieles are well developed, and form a regulär 

 arch into which a small, oval interclavicle entere. The ends of the clavicular arch are 



Fig. 277. 



Nothosaurus mirabilis, Münst. Muschelkalk ; Bayreuth, Ger 

 many. Dorsal aspect of pectoral arch, 1/5. d, Clavicle ; cor, Cora 

 coid ; icl, Interclavicle ; sc, Scapula. 



