276 MAZATLAN UNIVALVES 
the colour lighter than in C. incurva, and disposed to break up 
into spots; shaped like Emarginula rosea, with a very recurv- 
ed, distant and projecting vertex, a short, deeply sunk and 
slanting deck, and a hole above it passing up the spire. The 
characters are like some of the forms of Cr. incurva intensified ; 
and are subject to considerable variation. The mode of growth 
is as in that species; but the planorbiform vertical whirls 
are even smaller, (about ‘Ol across) with the apex deeply 
sunken. The smallest specimen is °15 in length; the largest 
found measures long. ‘84, lat.*62, alt. °46. 
A. flat sp. 52 © O62 ees a ee S18: 
The shortest-decked specimen measures ‘16 from deck margin 
to the posterior, °39 to the anterior end, with an apical projec- 
tion of °14. 
Hab.—Bodegas, California; attached to dead and living shells 
and to each other, 6-10 fm.; Hinds.—Straits of De Fuca, 
Gould.—Sta Barbara, Col. Jewett.— Panama, extremely rare, 
C. B. Ad.—Mazatlan ; extremely rare; [pool Col. 
Tablet 1857 contains 2 sp. very young. 1358, 1 sp. flat, 
margin extended.—1359, 1 sp. compressed, dark brown.—13860, 
the largest sp., twisted growth, slightly ribbed and corruga- 
ted.—1361, 1 sp. pale flesh colour. 
330MMBprerpcra IncurvA, Brod. 
Calyptrea (Crepidula) inecurva, Brod. Proc. Zool. Soc. 1834, 
p. 40 :— Trans. Zool. Soc. vol. i. pl. 29, f. 6—Miill. Syn. Nov. 
Test. Viv. p. 150. 
Crepidula incurva, B. MZ. Cat. D’ Orb. Moll. p. 49, no. 421.— 
C. B. Ad. Pan. Shells, p. 228, no. 347.—(Crypta i.) H. & A. 
Ad. Gen. 1. 369. 
=Crepidula hepatica, Menke, (non Desh. nec C. B. Ad. nec 
Krauss,) Zeit: f. Mal. 1847, p. 184, no. 33. 
This species is known normally by the sharp longitudinal 
ridges on the back, which are not dependent on the attachment, 
being regular in growth, and conspicuous when adherent on 
smooth shells. It is much smaller than C. onyx, of a deeper 
chocolate brown colour, convex, with the beak very prominent, 
smooth and black as in C. rugosa, Nutt. The epidermis is 
rather thin and deciduous. There are however so many speci- 
mens in which one or other of these characters pass away, that 
