s 



Raymond : Bkachiopoda and Ostracoda of thf. Chazv. 229 



lender spines. On the dorsal \alvc is a narrow depression, which is 

 most distinct at the lieak, and becomes obsolete on the anterior third 

 of the shell. The ventral valve shows an oval pedicle oi)enins a short 

 distance in front of the beak, and a narrow depression which extends 

 from the beak to the ojiening. 



Locality. — This species is rare, and has been found only at Valcour 

 Island and Chazy, New ^'()rk. The figured specimens are in the Yale 

 Universit\- Museum. 



Family CRAXID.l^. King. 

 Genus Petrockania nomen nov. 

 {Cranicllii (Ehlert, preoccupied.') 

 13. Petrocrania prona Raymond. 



(Plate XXXI\', figures 26-31.) 

 Crania prona R.-\vmond, 1906. Annals Carnegie Museum, Vol. Ill, p. 574. 



X'entra! valve flat or slightly convex, attached by a part of its surface 

 for at least a portion of its life. Dorsal valve depressed conical, sub- 

 rectangular in outline, usually wider than long. Apex near the posterior 

 margin not prominent. Surface marked by strong concentric lamellae, 

 which on some specimens turn upward, so that the surface is very rough, 

 while on others they are worn down so as to be indistinguishable. 



The muscle-scars are well shown in the brachial valves. Near the 

 posterior margin and somewhat widely separated are two narrow scars, 

 the posterior adductors. Half-way between the posterior margin and 

 the center of the shell are two prominent, elevated scars. These are 

 the anterior adductors. On the anterior outer margins of these 

 scars on some specimens fainter scar-like depressions may be observed. 

 These may be scars of brachial muscles, or they may be connected 

 with the vascular sinuses. Just in front of the center of the shell 

 of one specimen are two approximate scar-like impressions, the origin 

 of which is not evident. The vascular sinuses originate outside the 

 anterior adductors, extend to the front of the shell, and then turn 

 backward, following the margin nearly to the outer ends of the pos- 

 terior adductors. 



'Mr. Lambe has called my attention to the fact that Craniella was used for a 

 genus of sponges by O. .Schmidt in 1870 (Spong. Atlant. Gebiet., 66) and therefore 

 was not available when Oihlert used it for a brachiopod in 1888 (Bull. Soc. Etudes 

 Scientif. d'Angers, 37). I therefore propose to substitute the name Petrocrania, 

 with the same meaning as Craniella, OEhlert. 



