* 
220 F. B. Meek on the Family Pteriide. 
had thought a subgeneric name should be proposed. Farther 
comparisons, however, with specimens of some European speci 
species 
of this type, have led to the conclusion that these little shells 
form a section of the genus Humicrotis, probably too closely con- 
nected by some intermediate forms to merit a distinct subgeneric 
name. ‘The western species of this section alluded to above is 
ster: also Mf decussata, and M. Alberti Munster, (Goldf. Pe 
Germ., ii, p. 138-9,) as well as a species figured by Goldfuss as 
Monotis echinati, (id., pl. exxi, 6.) 
. + 
These shells have much the general outline of the typical spe , 
c 
cies of Humicrotis, being short or suborbicular and but very 
slightly oblique, without any anterior ear, and generally hay- 
ing the posterior ear much abbreviated. They differ, howevel, 
? 
n conclusion, I would remark that the numerous widely dif 2 
ferent types from the older rocks, figured in the various works 
In many cases, from microscopical examinations, in determining 
the family affinities of the ancient fossil genera of Avi . 
Arcide and Pectenide ; especially, where the condition of the 
Specimens under investigation is such as to prevent the Di 
of the hinge and interior from being determined. How far, 
ever, the different types of structure may have been cons be 
amongst all the ancient genera of these families, remains ' 
determined by the examination of a larger number of s 
the same, from co: i i f that species. 
the same locality paring our specimens with the type o: 8} ’ 
ature 
* The figures here referred to are not recognizable, but we know our shell to be | 
visi BP collected at 
pce 
eo Pea iene 
SG a 
