AET. 22 SAN PEDRO FAUNA OLDEOYD. 25 



slanting axial ribs, of which 14 occur upon the first, second, and 

 third, 16 upon the fourth, fifth, and sixth, 18 upon the seA^enth to 

 eleventh, and 22 upon the penultimate turn. These ribs extend quite 

 prominently to the summit of tlie whorls, wliich they render slightly 

 crenulated. The intercostal spaces are about as wide as the ribs, 

 terminating a little posterior to the suture, which leaves a narrow, 

 smooth band immediately above the well-constricted suture. Pe- 

 riphery of the last whorl well rounded. Base short, well rounded, 

 marked by the feeble continuations of the axial ribs, which evanesce 

 shortly after passing the periphery. The entire surface of the shell 

 is marked by fine, closely spaced spiral striations. Aperture broadly 

 oval; posterior angle obtuse; outer lip thin; inner lip slightly curved, 

 reflected over and appressed to the base for its anterior third, and 

 provided with an obsolete fold a little anterior to its insertion. 



Typ€.—C2it. No. 333506, U.S.N.M., has 12.5 whorls and measures: 

 length, 8.2 mm.; diameter, 2 mm. Cat. No. 352503 U.S.N.M. con- 

 tains another specimen showing the nucleus. 



Three additional specimens are in the Oldroyd collection. 



The present species belongs to the group of Turbonilla {Striotur- 

 honilla) dinora, panamensis, schjniUi, and htittoni. It is less robust 

 than T. (S.) dinora and has more ribs than that species, and is more 

 robust than any of the other members of the group. The fine spiral 

 striations have been omitted in the figure. 



TURBONILLA (PYRGOLAMPROS) COLLISELLA, new species. 



Plate 1, fig. 11. 



Shell moderatel}'^ large, elongate conic, yellowish, with a brownish 

 suffusion which probably indicates that when living it was brown. 

 Nuclear whorls two and a fifth, forming a somewhat depressed heli- 

 coid spiral, the axis of which is almost at right angles to that of the 

 succeeding turns, in the first of which the tilted edge of the nuclear 

 spiral is about one-fifth immersed. Early postnuclear whorls moder- 

 ately rounded, the later ones almost flattened, slightly shouldered at 

 the summit, marked by almost vertical axial ribs. Of these ribs, 

 which are much less strong and more numerous and more closely 

 spaced on the early whorls than on the later, where they become 

 senescent on the last turn, 24 occur on the second, 30 upon the third, 

 26 upon the fourth, 24 upon the fifth and sixth, 21 upon the seventh, 

 eighth, and ninth, 28 upon the tenth, while on the last whorl they 

 are decidedly irregular and irregularly spaced. The intercostal 

 spaces vary in width, being very narrow on the early turns, moder- 

 ately wide on the median and again on the later very narrow. Suture 

 moderately constricted. Periphery of the last whorl well rounded, 

 Base short, marked by the feeble continuations of the axial ribs. 



