194 The American Geologist. April, isao 
Of more than fifty species of gasteropoda described from the 
locality under consideration few have ever been figured ; and 
consequently much confusion has arisen regarding the proper 
identity of many of the forms. Recently, however, a very 
complete series was obtained. The majority of the species 
comprising this collection have been treated elsewhere ' with 
considerable detail and it remains now to consider more fully 
the forms of one of the most characteristic genera — Strap- 
arollus. 
The generic relations of Straparollus and Euomphalus have 
long been a subject of controversy. And, while the question 
can not at present be regarded as definitely settled, the 
evidence derived from all available sources points to the 
co-extension of the two genera. Each name was primarily 
proposed for a group seemingly quite distinct. But later 
inquiry has indicated that the alleged generic distinctions are 
actually more apparent than real ; and that the two sections 
can, with great propriety, be considered under a single term. 
Some recent writers have even proposed to make the two 
genera in question identical with Solarium established by 
Lamarck - for a group of modern gasteropods. But it does not 
appear feasible, nor advisable, to extend the limits of the 
Lamarckian genus as thus suggested ; while practically the 
separation of the recent and ancient forms is not diflScult and, 
as a matter of fact, is very convenient to the systematist. 
Straparollus, as defined by Montfort,' has for its type 
S. dionysii Mont. — a form with the spire somewhat elevated, 
the umbilicus broad and shallow, and the whorls regularly 
rounded. Euomphalus of Sowerby,^ represented by E. pent- 
angularis Sow., includes planorbiform shells having more or 
less distinctly angulated volutions. With the types alone 
under consideration the two groups might appear sufficiently 
well marked to warrant their generic separation. A more 
extended comparison, however, of the described species reveals 
no reliable criteria by which the two groups may be distin- 
guished. A further consideration of these resemblances and 
differences of divers individuals shows that they are so vari- 
'Keyes: Proc. Acad. Nat. Sci. Phila., 1889, pp. 284-298. 
- Syst. Anim. sans Vert., 1801 . 
•■' Conch. Syst., vol. ii, 1810. 
*Min. Conch., vol. i, 1814. 
