344 THE PORTLAND OOLITE PERIOD. CHAP. 



be incomplete at the anterior extremity to the extent of three 

 teeth. 



The teeth have the peculiarity of being marked by two strong 

 ridges passing from the apex, and dividing the crown or conical 

 surface into unequal spaces, the outer one widest, flat or but little 

 convex, and usually smooth. The fang is large and long, so that 

 a very large complete tooth may be as much as 6 inches long and 

 2 in diameter. 



Diagram CXXXVL Teeth of Pleiosaurus brachydeirus. Natural size. 



i. Young or posterior tooth, shewing one of the continuous cariniform striae on 

 the crown, and others which do not reach the apex. 2. Older and probably more 

 forward tooth ; the oarina roughly crenulated, with many striae which admit 

 of intermediate shorter ones near the base of the crown. The basal part of the tooth 

 expands much, and is hollow. There are often three cariniform striae proceeding 

 from the apex ; one, directed down the concave side, is usually shorter than the 

 others. On this side the striae are frequent ; on the convex face few or even none 

 between the carinae, but a smooth or rugulose space. 



Six or more of the cervical vertebrae near to the head have short 

 elliptical bodies, nearly plane on the articulating faces, with large 

 cicatrices on the sides, divided across, or rather a little obliquely. 

 The lower surface is swollen in the middle, sometimes prominent on 

 the anterior edge, depressed toward the sides, with two distinct 

 foramina. The cicatrices for the neurapophyses are inclined to each 

 other about 140, and deviate from the plane of the neural canal 

 30. That canal is striated lengthways, and expands at each end, 

 most so retrally there 1-35 inches broad. 



