BRACHIOPODA. 



153 



Genus CRANIELLA, (Ehlert. 1888. 



PI,ATE IV I, KIGS. I-IO. 



18S8. Craniella. CEhi.krt. Bull, do la Soc. d'Kliules scientif. d'An^crt;, p. 87. 1SS7. 

 1889. Craniella, Kayser. Abliaiidl. iler KOnig-l. Prcu.ss. geol. Lundesanstalt, Nciie Folge, Heft i, p. B'l. 

 Crania, in part, of sfivoral aiithdi-s. 



Diagnosis. " Shell somewhat irregular, outline subcircular or subquadraugu- 

 lar. Ventral valve thin, adhering by its entire sm-face ; dorsal valve conoidal, 

 more or less elevated ; apex subcentral, posterior ; interior of the dorsal valve 

 without a well defined border ; impressions of the 

 adductors large, very distinct, four in number, oi" 

 which the posterior two are quite distant, the two 

 subcentrals somewhat smaller, closely approximate 

 or even confluent; from near each of the posterior 

 impressions starts a vascular sinus, which is broad, 

 strongly sinuous near its point of dej^arture, nar- 

 rowing gradually in following the contour of the 

 valve, emitting from its marginal side dichotomiz- 

 ing secondary branches." ((Ehlert, loc. cit.) 



Type, Craniella Meduanensis, ffihlert. 



Observations. With the peculiar sigmoid vascular sinuses in the upper valve 

 as a distinctive character, we are disposed to regard this genus as well grounded. 

 This character is observed in an interesting species, Craniella Ulrichi, sp. nov., 

 from the Trenton limestones at Minneapolis, Minnesota, and in the common 

 Crania Hamiltonicz of the Hamilton shales, and undoubtedly will be found to be 

 far more generally distributed as tlie interior features of the palasozoic Cranias 

 become better known. To the degree of attachment of the lower valve we 

 should ascribe less importance than does Dr. OLhlert. The Trenton species 

 mentioned is sometimes attached and evidently as often free, while C. HamiltmicR 

 appears to be, like C. Meduanensis, invariably adherent l)y the entire surface of 

 the lower valve. 



7-*. CraniilUi Meduaiiensis. 

 Alter OinLEitr. 

 liitei-nal cast of upper \'alve. 



