CLASS GASTROPODA 
319 
umbones wide; diagonal areas hardly defined; sides ornamented with oval, 
flattened scales, large for the size of the shell, and in indistinct diverging 
series. Mucro small, situated in front. Color livid and olivaceous-brown 
variously stained. Plates of insertion at sides as in A. arragonites; anterior 
plate with five slits. (Carpenter.) (Tryon and Pilsbry, Manual of Con- 
chology.) 
Type in California State Collection, No. 1072. Type locality, Catalina 
Island, 10-20 fathoms. 
Range. Catalina Island, California, to Gulf of California. 
Described as Acanthochites avicula Carpenter. 
Genus KATHERINA Gray, 1847 
Valves two-thirds covered by the expanded girdle, the exposed portion 
divided into dorsal and side areas, instead of central and lateral. Insertion 
plates sharp, extremely long, thrown forward; that of the head valve with 
7-8 slits; sinus deep, spongy. Tail valve with a wide caudal emargination 
or sinus, and several slits, often partly obsolete, on each side. Girdle broad, 
smooth, poreless, leathery. Gills extending the whole length of the foot. 
(Tryon and Pilsbry, Manual of Conchology .) 
Type. C . tunicatus Wood. 
Distribution. Kamchatka, Alaska, Puget Sound, Catalina Island, 
California. 
Katherina tunicata Wood, 1815 
General Conchology, 11; PI. 2, fig. 1. Tryon and Pilsbry, Manual of Conchology , 
15:41; PI. 1, figs. 1-11. 
Ch. testa octovalvi laevi, valvis albis, supra membranis suborbicularis, 
limbo coriaceo reflexo. 
Shell of eight valves, smooth, valves white, above the membrane 
roundish, margin coriaceous and turned back. (Wood.) 
This singular shell makes a very different appearance from any other 
species of the genus. The valves instead of being wholly visible, are coated 
halfway upward with a black membrane, which is reflected from the 
coriaceous border, and fixed into a groove cut for that purpose round the 
upper part of each valve. This portion that is seen above the membrane, 
is roundish, uneven, and emarginate, of a sordid white or flesh color, and 
collectively resembling a row of dried beans. The remains of a thin cortical 
substance is to be seen on parts of the naked shell, which, independent of 
the coriaceous membrane, once covered the valves. The valves within 
are quite exposed and perfectly white. Length, 4; breadth, 1% in. (Wood.) 
[921] 
