366 DESCRIPTIONS OF NEW SPECIES OF FOSSILS 



CALLIOSTOMA, Sw. 

 (Zizyphinus, Gray.) 

 C. GUPPYANA, Gabb, n. s., PL 46, fig. 63. 



Shell small, conical ; spire elevated ; whorls eight or nine ; the first one, or one 

 and a half nuclear and unornamented. Suture hardly distinguishable among the 

 numerous ribs. Sides of the whorls regularly sloping, so that the whole apical 

 slope is a straight line. Surface of each whorl ornamented by four large beaded 

 Tibs, one placed at the extreme upper margin, two c^ose together below, and the 

 fourth about half way between the upper of these two and the top rib. The two 

 upper ribs are accompanied on the body whorl, each by a smaller one, placed a 

 small distance below it, and all the beading on all these ribs is placed along the 

 lines of growth and connected by small raised lines. The outer basal angle of the 

 body whorl is acute; the under surface flat to concave, and ornamented by many 

 small revolving ribs. 



Height of shell 5 mm. 



GIBBULA, Risso. 



G. TUBERCULOSA, d'Orb, sp. 



Delphinula id., d'Orb, La Sagra, vol. 2, p. 69, PI. 19, figs. 28-30. 



MARGARITA, Leach. 

 M. TRIOARINATA, Gabb, PI. 46, fig. 64. 



Shell small, robust, spire elevated, whorls four — the one at the apex round, the 

 others angulated and ornamented. Top of the whorls sloping, sides flat and ver- 

 tical. Suture impressed and bordered by the strongly crenulated margin of the 

 succeeding whorl. Top of whorl between this margin and the outer angle either 

 plain or carrying one or more small ribs. Periphery of whorl carrying three strong 

 crenulated ribs, the interspaces either perfectly plain or with faint interpolated 

 ribs ; all this covered with very minute lines of growth. Under surface also varia- 

 ble. In one case before me it is perfectly plain ; in another it is closely covered 

 with minute, revolving, beaded ribs. The umbilicus varies greatly in diameter, is 

 invariably bordered by a crenulated angle, the crenulation fiae or coarse according 

 to variation ; and half way up on the whorl it carries a strong, spiral, revolving rib. 



Average height 2| mm. 



First rather imperfectly described from Santo Domingo, but now that I have 

 a fine series from Costa Eica showing all the above, and even other minor varia^ 

 tions, I have availed myself of the opportunity of redescribing it. 



