MARGARITA. 305 



within. Inner lij) strong, concave, patulouhJ, tliickened and angu- 

 lated at point of the ])illar where tlie umbilical keel joins it. Uni- 

 bilicus funnel-shaped, pervious ; a deeply marked suture coils up 

 within it. 



Alt. 0-46 in., diam. 0-46. Penultimate whorl, height 0-14. Mouth, 

 height 0-25, breadth 0-23 in. ( Watson.) 



This is a singularly beautiful shell. It is connected in a general 

 way with the group to which Trochus (6xystele) euspira, Dall. 

 (Proc. Zool. Soc. Lond., 1883, p. 98, pi. xx, fig. 6) belongs. In that 

 species the umbilicus is large when the shell is young, and fills up 

 entirely when the shell is full grown. ( Watson.) 



S. E. of Philippines, 500 fms. 



T. (Margarita) streptophorus Watson, Challenger Gasteroj)., p. 

 91, t. 17, f. 4. 



M. sciNTiLLANS AVatsou. PI. 64, fig. 62. 



Shell small, thin, white, very depressedly conoidal, angulated, 

 tumid on the base, umbilicated ; mouth semioval. Sculpture : It 

 is perfectly smooth but for some curved puckerings which radiate 

 from the umbilicus, but very soon die out; above the middle the 

 body-whorl is roundly angulated. Color pure white, with a trans- 

 parent calcareous layer over brilliant fiery pearly nacre. Spire very 

 depressedly conical. Apex bluntly rounded, with a minute hyaline, 

 depressed embryonic tip. Whorls 4' barely convex. Suture slightly 

 impressed. Mouth semi-oval. Outer lip thin, barely angulated at 

 the periphery. Pillar-lip straight, patulous, right-angled at its 

 junction with the l)ase. Umbilicus small. 



Alt. 0-14 in., diam. 0-2, least 016. Penultimate whorl 0-025. 

 Mouth, height 0*09, breadth 0-11. ( Watson.) 



The specimen from which I have described this is neither full 

 grown nor perfect, but the species is a ver}^ well-marked one. It is 

 much more depressed and has the whorls less rounded than Trochus 

 (Margarita) euspira, Dall. Than Trochus helicinus, Fabr., it is 

 much more depressed, much more brilliantly nacreous, and the 

 surface is much more polished, and the radiating puckers are nuich 

 .stronger. ( TFatsox.) 



Off Culebra Id., W. hid., 390 fms. 



T. (Margarita f) scintiUans Watson, Journ. Linn. Soc. Lond. 

 xiv, p. 712 ; Challenger Kept., p. 91, t. 5, f. 2. 

 20 



