D2 MARINE BIOLOGY OF THE SUDANESE RED SEA. 
two ribs on the lateral areas in place of four, and the tail-valve is concave 
behind, not convex as described by him and shown in his figures. The 
var. savignyi, founded on a figure of Savigny’s, appears to differ in having 
a smooth central area, with fewer ribs on the head- and tail-valves. I have 
described the ribs on the head- and tail-valves as seen by me, but I would 
not place great reliance on the actual number, since they appear to be liable 
to split up. 
CRASPEDOCHITON LAQUEATUS (Sowerby). 
Chiton laqueatus, Sowerby, Proc. Zool. Soc. 1841, p. 104. 
Craspedochiton laqueatus, Sby.; Pilsbry, Man. Conch. vol. xiy. p. 285. 
Hab. Zanzibar Channel, 10-20 fath. ; also in 5 fath., bottom gravel, broken 
shells, &e.: Wasin, shore and in 10 fath. 
A single specimen from each locality. Im my view they are all varying 
forms of this well-known shell, which, described from the Philippines, has been 
since identified from Ceylon and the Maldive Is. I have been unable to attach 
any of these specimens to the recently described C. tessellatus, Nierstrasz. It 
must be borne in mind that the shape of the girdle, &c., varies with the mode 
of preservation. 
ACANTHOCHITES NIERSTRASZI, 0. sp. 
Shell elongate, moderately elevated, subcarinate. Surface dull, the median. 
area of the central valves white or pinkish, the residue of the valves more or: 
less, irregularly, marked with blackish brown, as are also the anterior and 
posterior valves. 
Median valves somewhat beaked. Dorsal area well-marked, fairly large in 
size and longitudinally striate. Latero-pleural areas covered with large flat 
granules, these being rounded towards the beaks and becoming pear-shaped 
towards the outer margin. The tegmentum of posterior valve is subquadrate, 
the muero central. 
Interior whitish, sinus moderate in size. Slits as usual in the group. 
Girdle yellowish-white to brown, large, covered with closely-set hairs ; 18 
small white tufts of spicules are present, four being in front of the anterior 
valve, and they arise from greenish pores. 
Length about 28, breadth about 18 mill. 
Hab. Suez mud-flats ; Dock wall at Suez. 
Akin to A. penicillatus, Desh., but apparently differing from that species in 
the following characters. The sculpture in the new species is a trifle coarser, 
the granules not so “regularly” arranged and being rounder near the beaks ; 
the tegmentum of the posterior valve is not rounded, being angular, and the 
mucro is ventral, not posterior. 
I have been unable to trace any “ fringe of long peripheral spines” in the 
present form. 
