I '1 P LEUIt' >TO:IA RIID.E-HALIOTID.K. 



P. ADAXSOXIANA Crosse & Fischer. PL 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 unibilicated, 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 stria? and two spiral, slightly 

 marked series of granules; last whorl obtusely bicarinate; slit 

 fascicle with semicircular, delicate, impressed stride. Aperture sub- 

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



Of Barbados, in 69-200 fins. ; Guadelupe, 150 fms. 



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

 2, 1861. DALL, Bull. M. C. Z. ix, p. 78, 1881. CKOSSE, 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 Kept. Blake 

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

 SOWERBY in Conch. Icon.,f. 1, J874. 



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 HALIOTID^E. 



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, colti- 

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

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



