50 
4. Johannes Boehm, Inoceramus Cripsi auct. 
figures a form possessing it, which he regards as belonging to /. 
cripsii Mantell, and also refers others to the same, apparently 
regarding it as only an abnormal feature and not of specific value. 
Still in his description of the figure on Plate VII, he applies to 
the shell the varietal name sulcatu-s , descriptive of this very fea¬ 
ture. Mr. Meek also mentions its existence on specimens which 
he refers to I. cripsii var. barabini , but which are probably dis- 
tinct from that form and identical with one of those above re- 
ferred to. Some authors, liowever, have considered it of more im- 
portance. Mons. d’Oebigny founded his I. impressus on the 
existence of this feature in his types, and Dr. Morton’s 1. alveatus 
is another example. Considering the development of this feature 
to so great an extent, and in several species, not only in America 
but also in Europe and elsewhere, we deem it other than an ab¬ 
normal or accidental one, and not only of specific importance, but 
as marking a distinct generic group, and propose for it the generic 
name Endocostea, under the impression and belief that it marks 
the line of recession of the larger or posterior muscular scar, as 
in the forms of Inoceramus on which this scar has been detected 
it occupies the same relative position.« 
Whitfield charakterisiert seine Gattung in nachstehender 
Weise: 
Shell resembling Inoceramus, being bivalve, with both 
sides convex, but more or less unequal, and composed of 
two layers, an outer vertically fibrous coating and an inner 
nacreous or pearly lining; hinge line straight, edentulous, 
with a narrow linear external cartilage area on each valve. 
Valves provided with an oblique internal rib passing from 
behind the beaks, along the postero-cardinal slope, toward 
the postero-basal margin, marking the position of the 
posterior muscular imprint; other muscular markings un- 
known. Type, E. typica Whitf. 
We have not been able to detect the anterior muscular scar 
or pallial line, except the latter as au irregulär transverse line of 
small tubercles across the beak of internal casts in several cases, 
and a slight curving ridge, faintly marked on a smaller number 
