INSTITUTE OF SCIENCE, PHILADELPHIA. I29 



ond gradually acquiring close-set, concavely arched, transverse riblets; subse- 

 quent whorls showing between the sutures about five strong threads, with wider 

 interspaces, overrunning nine well-marked round ribs, extending from suture 

 to suture ; on the last whorl the ribs become more or less obscure, the spirals 

 more numerous and less elevated, and the whorl shows a tendency to con- 

 striction in front of the suture; whorls rounded, suture appressed, undulated 

 by the ribs; canal moderate, recurved, striated sparsely behind; aperture 

 ovate, outer lip simple, sharp, without internal lirse; inner lip smooth, con- 

 cave, not callous. Max. Ion. of shell 12.0; of aperture 6.0; max. diam. of shell 

 5.0 mm. 



Silex-beds at Ballast Point, rare. 



The figure was drawn from a less perfect specimen than that from which 

 the description was subsequently secured, and does not show the strength of 

 the sculpture on the upper part of the spire, the curvature of the canal, or its 

 constriction at the base as clearly as desirable. It is, however, very consider- 

 ably magnified. 



Genus PISANIA Bivona. 



Subgenus Tritonidea Swainson. 



Tritonidea pauper n. s. 



Plate 4, figure 8 c. 



Shell small, with one and a half smooth nuclear, and about five subse- 

 quent whorls ; transverse sculpture of numerous (11-16) broad, close-set, low, 

 rounded riblets, which become obsolete in front of the periphery, are slightly 

 concave in the direction of growth, and on the spire extend from suture to 

 suture ; spiral sculpture, on the early whorls, of three primary cords, one near 

 the suture, the other two near the periphery, between which finer ones are 

 gradually intercalated ; these override the riblets and, at first, become rather 

 nodulous at the intersections, but on the last whorl the spirals have become 

 more numerous and cover the whole whorl without nodulation, and generally 

 alternate in strength ; canal short, recurved ; apertural varix well marked ; 

 aperture subovate, outer lip internally dentate, with three especially marked 

 anterior teeth (not well shown in the figure) ; inner lip reflected, more or less 

 granulous ; pillar keeled at its anterior end ; the whorls are moderately rounded 

 and the suture very distinct. Max. Ion. of shell 9.5 ; of aperture 5.0; max. 

 lat. of shell 5.0 mm. 



Miocene of Ballast Point, in the silex-beds, rare. 



This pretty little species belongs to the group of which, among recent 

 forms, T. Orbignyi Payr. is an example. The latter is both Mediterranean and 

 Floridian, and this would indicate some antiquity for the race. 



The figure, otherwise good, does not show well the nascent granulations 

 on the pillar or the little teeth inside the outer lip, but the peculiar condition 

 of the pseudomorph rendered it particularly difficult for the draughtsman to 

 make out these characters. 



