180 PALEONTOLOGY OF NEW JEESEY. 



pose that this feature of the vokitiou left an impressed band on the inside 

 of the shell which was subsequently filled, partially or entirely, by the 

 deposit of shelly matter on the inside as the shell increased with age and 

 size, and that the openings were closed beyond the outer half of the last 

 volution. 



Pleurotrema solariformis, n. sp. 

 Plate XXII, Figs. 10-14. 

 Archiiectonica Abbottii in part of Gabb: Proc. Acad. Nat. Sci., Phila., 1861, p. 331. 



Shell of more than moderate size, the largest example before me meas- 

 uring almost 2 J inches in its greatest diameter, by 1^ inches in height, and 

 is an internal cast with the apical volutions absent. Volutions as preserved 

 in tliis specimen, four in number, and probably one and a half or two 

 absent; spire low, conical, the sides forming an angle of about 90°, and 

 the volutions flattened on their upper surfaces in a line with the apical 

 angle; sutures well marked but not deep, indicating a shell of only mod- 

 erate thickness ; base of the volutions flattened-convex, leaving the periph- 

 eral angle somewhat acutely rounded; the inner part of the base of the 

 volution rapidly slopes into the broad, open perspective umbilicus, forming 

 a rounded funnel-shaped cavity in which all the volutions are seen, but 

 with a very slightly marked suture line separating them. Section of the 

 volution rhombically elongate-ovate, the umbilical part being attenuated 

 where it joins the preceding volution; along the middle of the outer volu- 

 tion there occurs an elevated ridge, which presents the appearance of a 

 series of interrupted nodes of an elongate-oval shape, as if the shell had 

 been provided with a line of oval openings occupying this position, but 

 filling up beyond the outer half of the volution; surface of the shell 

 unknown. 



This shell possesses much the appearance of a Solarium, but the over- 

 lapping of the outer volution upon the base of those preceding it is a 

 marked and distinguishing feature; while the absence of angle bounding 

 the umbilicus at once separates it from that genus. The species has been 

 confounded in the collection Acad. Nat. Sci., Phila., with Pleurotomaria 

 Abbotti, from which it differs very decidedly, evea more thaa generically. 



