122 



GENERA OF THE SUBORDERS ORTHOIDEA AND PENTAMEROIDEA 



Genus CARINIFERELLA Schuchert and 

 Cooper 1931 



(Lat. carina, keel; and jerre, to bear) 

 PI. 18, figs. 9-12, 15, 16 

 Schuchert and Cooper, Amer. Jour. Sci. (5), vol. 22, 1931, 

 p. 246. 



Genoholotype. — Orthis carinata Hall 1843, 

 Geol. N. Y., Rept. Fourth Dist., p. 267, fig. 1, as 

 figured by Hall and Clarke (1892). 



Description. Exterior. — Transversely semicir- 

 cular, margins rounded, cardinal angles obtusely 

 rounded; hinge-line narrower than the greatest width 

 of the shell; lateral profile convexo-concave to une- 

 qually biconvex; anterior commissure sulcate; fold nar- 

 row, subcarinate; sulcus deep, narrow ; ventral inter- 

 area short, apsacline, beak not prominent, incurved, 

 umbo low, convex, and sulcate. Ornamentation mul- 

 ticostellate, with elevated growth-lines covering the 

 whole surface. Test fibrous, punctate. 



Ventral interior. — Delthyrial cavity deep; teeth 

 strong; dental plates thick, nearly obsolete in adults; 

 muscle field bilobed in front; diductor scars elongate, 

 expanded anteriorly; adductor track linear, not en- 

 closed in front by the diductor scars. Aggregate 

 adductor scar elliptical. Adjuster scars narrow, diver- 

 gent, short, placed posterior to the diductor impres- 

 sions. Short pallial sinuses extending antero-laterally 

 for a short distance in front of the diductor scars. 



Dorsal interior. — Cardinalia confined to the imme- 

 diate vicinity of the hinge, sockets deep, oblique; brach- 

 iophore plates widely divergent and extending verti- 

 cally to the floor of the valve, without fulcral plates; 

 cardinal process very small, shaft short, myophore 

 trilobed; median ridge low, extending to the anterior 

 margin of the muscle area where it merges into the 

 fold produced by the ventral sulcus. Muscle area 

 small as a whole, not extending to the middle of the 

 shell. Adductor scars separated by horizontal ridges; 

 anterior adductors the smaller. 



Geologic range. — Upper Devonian. 



American Species 



Orthis carinata Hall 1843 



DalmaneUa carinata efsilon Williams 1908 



D.elmiraW\\Yi3.m.% 1908 



Z). /io^a Williams 1908 {non Hall 1867) 



D. Virginia Williams 1908 



D. Virginia beta Williams 1908 



European Species 



Carinijerella dumonti (Verneuil) 



Distinguishing characters. — The distinctive 

 features of this genus are the convexo-concave profile 

 of the shell, the aberrant sharp fold and the corre- 

 sponding deep, narrow sulcus, the Dalmanella-WVt ven- 

 tral musculature, the strongly divergent brachiophore 

 plates, and the small muscle area of the dorsal valve. 



Discussion. — The members of this new genus have ' 

 been referred variously to Schizophoria and Dalman- 

 eUa. Schuchert referred them to the former in 1897, 

 but in 1908 Williams®^ restudied the different species 

 and concluded that their affinities placed them in clos- 

 est association with DalmaneUa. The combination of 

 characters displayed by this group, however, necessitates 

 the creation of a special designation for them. 



The ventral musculature is similar to that of Dal- 

 maneUa and Schizophoria in the anterior bilobation, 

 but the adjuster scars are much shorter and more 

 oblique, and the median ridge (euseptoid) common to 

 the Upper Devonian Schizophorias is not well devel- 

 oped. Instead of being strongly elevated and con- 

 tinued in front of the diductor scars as a ridge, it is 

 divided in Carinijerella and forms a distinct V in front 

 of the diductors. Williams considers this forked 

 septum an important character of the genus "Dal- 

 manellt^' although it is by no means common to all 

 the "species." 



In the dorsal valve the variations of this genus from 

 Schizophoria are most readily perceived in the nature 

 of the cardinalia and the musculature. The brachio- 

 phore plates are widely divergent, bladelike, attached 

 directly to the inner surface of the valve. The sockets 

 are wide and elongate and are not defined by a fulcral 

 plate as is so characteristic in Schizophoria. The mus- 

 cle area is rather small, but the fact that the individual 

 scars are separated by a horizontal ridge contrasts with 

 Schizophoria in which the scars are separated by an 

 oblique ridge. In this respect Carinijerella resembles 

 the genus Proschizophoria most closely. The adductor 

 scars of Schizophoria, furthermore, are usually larger 

 and somewhat flabellate. Pallial markings are very 

 indistinct in most of the specimens, but when visible 

 show the same elements common in the genus Levenea. 

 There is a lateral trunk extending slightly obliquely 

 from the ridges separating the adductors and another 

 pair extends forward from the antero-median ex- 

 tremity of the anterior adductors. In Carinijerella 

 dumonti the anterior trunks bifurcate near their point 

 of origin so that there are four trunks originating in 

 the same points as the pallial sinuses of Levenea. Car- 

 inijerella is evidently an Upper Devonian branch of 

 the Dalmanellidas, aberrant chiefly in its external form. 



Genus AULACELLA Schuchert and Cooper 

 1931 



(Gr. atihx, furrow) 

 PI. 19, figs. 7, 8, 10, 11, 13 



Schuchert and Cooper, Amer. Jour. Sci. (5), vol. 22, 1931, 

 p. 246. 



Genoholotype. — Orthis eijelensis de Verneuil 

 1850, Bull. Soc. Geol. France, 2d ser., vol. 7, p. 25. 



^^ Proc. U. S. Nat. Mus., vol. 34, pp. 38-41. 



