NATURAL SCIENCES OF PHILADELPHIA. 17 



there are no traces of a band, as in Pleurotomaria. This character would pro- 

 bably place the species in the group for which the name Schizostoma was pro- 

 posed by Bronn, but palaeontologists have generally regarded the type foi 

 which that name was proposed, as not being sufficiently distinct from Euom- 

 phalns to be retained as a separate genus. 



Associated with the above, a single specimen was found, of the same size, 

 and agreeing very closely with that from which the foregoing description was 

 drawn up, but differing in being proportionally wider, and not so oblique on 

 the periphery, which is also more convex in the middle. The angle of its 

 under side also differs in being a little farther in from the outer margin, and 

 directed downward, instead of outward, while its umbilicus is proportionally 

 deeper. This may be a distinct species, but without more specimens for com- 

 parison we do not feel willing to regard it as being entitled to a separate 

 name. 



These shells, including E. rugosus, Hall, and E. catilloides, Conrad (sp.), are 

 related to E. quadratus of McCoy, from the Mountain Limestone of Ireland, 

 though sufficiently distinct specifically. At one time we were inclined to think 

 that E. rugosus, Hall, and E. catilloides, Conrad, together with a few others, 

 should be separated from Euomphalus, under a distinct generic name ; but 

 after seeing the large species we have here described, which so closely connect 

 these little shells with such forms as E. pentangulaius and E. catillus, upon 

 which the genus was originally founded, we can no longer doubt that all of 

 these shells really belong to one genus. This series of intermediate forms 

 connecting the small, nearly planorbicular species mentioned above with the 

 typical forms of Euomphalus, shows clearly that none of the former belong to 

 the articulate genus Spirorbis, as has been thought by some, but that they are 

 really true mollusks. 



Locality and position. Upper Coal Measures, Montgomery County, Illinois. 

 Collected by Mr. G. C. Broadhead, of the Illinois Geological Survey. 



Subulites inplatus, M. and W. 



Shell very ventricose, subfusiform ; volutions about five and a half to six, 

 those of the spire moderately convex in the (external?) cast; last one very 

 large, ventricose, and composing much the larger part of the whole, produced 

 and contracted below so as apparently to terminate in a short canal ; aperture 

 narrow, rhombic and poiuted, or angular above and below; suture well de- 

 fined in the cast ; surface unknown. 



Height of a specimen with apparently about two whorls at the apex, and 

 portions of the lower extremity of the produced body whorl broken away, 1-85 

 inches; breadth of body volution, about 1-15 inches. 



It is barely possible that this may be a ventricose, fusiform Murchisonia, as 

 we only know it from rough casts, apparently of the exterior. As it shows 

 no traces, however, of any revolving band or line, and has much the general 

 physiognomy of Subulites,\e have concluded to refer it provisionally to that 

 group. 



Its most marked character is the large size and very ventricose form of its 

 body volution, in which it resembles some of the Carboniferous species of M- 

 crocheilus. It differs from these, however, in the produced and subcanaliculate 

 peculiarity of the lower part of its body whorl. 



Locality and position. Galena beds of the Lower Silurian : Carrol County, 



Illinois. 



CEPHALOPODA. 



Genus NAUTILUS, Auct. 



Subgenus SOLENOCHILUS * M. and W. 



We propose the above name for a group of Nautili which we believe to be 



* <ra>x>tv. a channel; ^Ci\q^ hp- 



1870.] 



