xiii. ICHTHYOSA UR US. 339 



Indications of other species of Ichthyosaurus in the Kimmeridge clay. 



ICHTHYOSAURUS DILATATUS. n. s. 



A considerable number of dorsal and caudal vertebrae have a 

 greater proportionate breadth than the corresponding bones in 

 Ichthyosaurus trigonus, and some difference of outline of the faces. 

 No other particular distinction appears constant. None of them 

 have the exceptionally concave space about the centre of the face. 

 They are thicker than the corresponding vertebrae of Ichthyosaurus 

 thyreospondylus. In the preceding chapter the characters of the 

 cervical vertebrae are considered. 



, w ICHTHYOSAURUS OVALIS. n. s. 



Other vertebrae of the anterior dorsal, posterior dorsal, and 

 anterior caudal series have an oval outline of face, and are higher 

 than broad. Two of the posterior dorsal vertebrae have the cica- 

 trices placed very low on the body, the lower and smaller one quite 

 on the anterior edge, in the situation occupied by the haemapophysis 

 of a crocodilian reptile. These specimens are from Swindon and 

 Shotover. Another, of similar general aspect, comes from Kim- 

 meridge in Dorsetshire. 



Length of a posterior dorsal, 1*25 ; breadth, 2*85; height, 3*05. 



ICHTHYOSAURUS ^EQUALIS. n.s. 



One caudal vertebra, remarkable for neatness, is peculiar in the 

 position of the single prominent excavated lateral apophysis, for 

 it is placed almost exactly half-way on the body, or in the middle 

 of the side. It is short, with flattened faces deeply excavated round 

 the centre. Locality Shotover. 



I 



ICHTHYOSAURUS OR POLYPTYCHODON. 



This remarkably conical tooth, with numerous regular nearly equal 

 striae drawn down its sides, has a largely expanded base and a central 

 replacement. To which of the systems of vertebrae occurring at Shot- 

 over it belongs, if to any, there appears no method of determining. 



