72 PLEU IlOTOilA RIIDvE-HALIOTJDiE. 



P. adaxsoniana Crosse & Fischer. PI. 56, figs. 1, 2, 3. 



Shell trochiform above, plano-convex beneath, and concave in 

 the middle, concentrically costate-sulcate, the ribs granulose ; 

 broadly and deeply umbilicated, the umbilicus pervious ; longitu- 

 dinally rugulose ; color pale yellowish-fleshy, with numerous, irregu- 

 lar, reddish spots, sometimes vivid, sometimes more or less effaced ; 

 apex acuminate, smooth, yellowish ; whorls 11, slowly increasing, 

 rather planulate at the sutures ; unequally divided by the slit fas- 

 ciole, below it traversed by 7 to 8 spiral granose ribs, above it with 

 longitudinal, oblique, rather separated striae and two spiral, slightly 

 marked series of granules ; last whorl obtusely bicarinate ; slit 

 fasciole with semicircular, delicate, impressed striae. Aperture sub- 

 quadrate, pearly within. Alt. 74, diam. 80 mill. (C. & F.) 



Off Barbados, in 69-200 fms. ; Guadelupe, 150 fms. 



P. adansoniana C. & F., Journ. de Conchy 1. ix, p. 163, t. 5, f. 1, 

 2, 1861.— Dall, Bull. M. C. Z. ix, p. 78, 1881.— Crosse, Journ. 

 de Conchyl. xxii, p. 12, t. 1, f. 1, 2, 1882.— Dall in Agassiz, Three 

 Cruises of the Blake ii, p. 69, f. 288, 1888 ; and in Rept. Blake 

 Gasterop., p. 400, t. 30, t. 31, f. 3-6, t. 32, f. 10, t. 37, f. 4, 1889.— 

 Sow t erby in Conch. Icon., f. 1, 1874. 



Two specimens dredged by the Blake measure as follows: 



a. Alt. 130, diam. 130 mill. ; length of slit, 200 mill. 



b. Alt. 70, diam. 88 mill. ; length of slit, 142 mill. 



The operculum as described by Dall, measures 54 mill, x 47 mill., 

 is almost flat, with 10 whorls of which the central ones are rather 

 indistinct. The outer surface is minutely sharply spirally striated, 

 and a central spot the size of a pin head is indistinctly indented ; 

 the inner side is polished and shows a somewhat egg-shaped scar of 

 attachment ; it is of an amber-brown color. The extreme margin is 

 thin and a little frayed. The anatomy and dentition are described 

 and figured by Dall, in the Blake Report. 



Family HALIOTIDJE. 



Family characters. 



Shell nacreous, spiral, the spire small, body-whorl very large and 

 depressed, having a row of round or oval holes along the left side, 

 aperture very large, occupying nearly all of the lower face, colu- 

 mella (properly speaking) absent, the spire being open in the middle, 

 seen from below ; but the columellar margin is produced into a 



