BRACHIOPODA. 
153 
Genus CRANIELLA, (Ehlert. 1888. 
PLATE IV i, FIGS. 1-16. 
1888. Craniella, GEhlert. Bull, de la Soc. d’Etudes scientif. d’Angers, p. 37. 1887. 
1889. Craniella, Kayser. Abhandl. der Konigl. Preuss. geol. Landesanstalt, Neue Folge, Heft i, p. 65. 
Crania, in part, of several authors. 
Diagnosis. “ Shell somewhat irregular, outline subcircular or subquadrangu- 
lar. Ventral valve thin, adhering by its entire surface; 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, of 
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 departure, 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, (Ehlert. 
Observations. With the peculiar sigmoid vascular sinuses in the upper valve 
a.s 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 Hamiltonw of the Hamilton shales, and undoubtedly will be found to be 
far more generally distributed as the interior features of the palaeozoic Cranias 
become better known. To the degree of attachment of the lower valve we 
should ascribe less importance than does Dr. (Ehlert. The Trenton species 
mentioned is sometimes attached and evidently as often free, while C. Hamiltonia 
appears to be, like C. Meduanensis, invariably adherent by the entire surface of 
the lower valve. 
Fig. 72. Craniella Meduanensis. 
After GEhlert. 
Internal cast of upper valve. 
