394 MEMOIRS OF THE CARNEGIE MUSEUM. 



new species, and it seems proper to associate under the latter head the small 

 shark, which von Zittel regarded as the young of C. falcifer."^ 



2. Cestracion zitteli Eastman. (Plate LVII, fig. 1.) 



1911. Cestracion zitteli C. R. Eastman, Amer. Journ. Sci. (4), Vol. XXXI, p. 401, 

 pi. I. 



Type. — Nearly complete skeleton; Carnegie Museum (Cat. No. 4423). 



"The example, which is here regarded as typifying a distinct species, merits 

 special attention on account of its being probably the most perfect post-Liassic 

 Cestraciont shark, which has thus far been discovered in the fossil state. Agreeing 

 in principal characteristics with the small form described by von Zittel as the 

 young of C. falcifer, as above stated, its features are nevertheless judged to be 

 sufficiently distinctive to warrant a separation from that species. 



"The more important differences relate to the position of the dorsal fins, 

 form and relative size of the dorsal fin-spines, number and size of the vertebral 

 centra, and presence of a series of enlarged, radially ridged, and acutely conical 

 shagreen tubercles along the back. A comparison of characters displayed by the 

 dentition in the type-specimen is impossible, as the teeth are unfortunately not 

 preserved, but in the small Munich example, which may be with entire propriety 

 associated with the type now under description, the lateral teeth are said to be 

 'mit einer Anzahl von Zacken versehen.' This may be understood to mean that 

 the oral surface is faintly rugose, transversely striated perhaps, or else that the 

 coronal margin is slightly indented. In anj^ case, however, the teeth must have 

 been exceedingly minute. 



"A summary of the chief features of interest presented by the type-specimen 

 may be given as follows : Form of body slender and elongate ; total length from 

 extremity of snout to that of the vertebral column about 15 cm. Vertebral centra 

 varying somewhat in length, being more compressed in a longitudinal direction 

 underneath the second dorsal fin. About twenty-five centra occupy the interval 

 between the bases of the two dorsal fin-spines, and it is noteworthy that these 

 latter abut almost directly against the column. . . . The spines themselves are 

 of relatively large size, smooth, sharply pointed distally, and only slightly arcuate 

 or recurved."'* They were evidently deeply implanted in the soft parts, but have 

 become to a slight extent displaced from association with the front margin of the 

 fins prior to fossilization. 



' Eastman, I. c. 



* Eastman, C. R., Am. Jour. Sci. (4), Vol. XXXI, 1911, p. 401. 



