1888.] NATURAL SCIENCES OF PHILADELPHIA. 245 



composed more than one-third of the entire fauna. Not only did 

 they exceed in species but they far outnumbered all others in indi- 

 viduals, and while as a rule they were small and some of them even 

 minute their great numbers made up, in great part at least, for the 

 conspicuity of larger but few forms. Though the majority of the 

 forms of this group are small it is not a depauperation as among the 

 brachiopods, as is shown by the average size of the individuals of 

 each species being normal, and in some instances even considerably 

 above. Some of the species are also of interest because of their 

 recognition for the first time within the limits of the state, and thus 

 to a considerable extent their known geographical range is increased. 

 Others of the species enumerated are now known to have a wide 

 geographical distribution which is suggestive of a somewhat ex- 

 tended vertical range. Among recent mollusca and especially land 

 forms a wide geographical distribution, as has been remarked by 

 Binney, appears to be indicative of a high antiquity for the group. 

 The corroborative evidence is abundant : a notable instance is the 

 living Zonites, four or more species of which are circumpolar in their 

 distribution; and the genus — even a subgenus Conulus to which 

 one of these living forms belongs — ranges back to the carboniferous, 

 Avhile the genus Pupa is represented in the carboniferous by four 

 species. Cephalopods are not abundant in the region under consid- 

 eration and are represented by only two genera and five species, yet 

 a Nautilus attained a diameter of twenty centimetres, and an Or- 

 thoceras was fifty centimetres in length with a diameter at the 

 larger extremity of five centimetres. Of the lamellibranchs the 

 majority are small, though two of them are comjiaratively large, 

 attaining a length of nearly ten centimetres, yet having an extremely 

 thin and fragile shell. One of the specimens collected is of especial 

 significance as exhibiting in all its details the intetnal features of 

 the shell— the characteristic well-defined muscular scars and the 

 edentulous hinge margin ; in fact, so closely does it resemble in 

 these characters, the general form and external appearance, a mod- 

 ern Anodonta that it is difficult to see how it can be generically 

 separated from it ; and should further investigation prove that the 

 specimens under consideration really belong to that genus, it would 

 be of unusual interest in its bearing upon the distribution of fresh- 

 water or non-marine mollusca during geologic times. The modern 

 TJnio and allied genera certainly have both a wide geographical and 

 geological distribution, as is shown by the rich discoveries of Union- 



