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hk. R. SYKES—-REPORT ON THE POLYPLACOPHORA. al 
Reports on the Maring BroLoey of the SuDANESE RED SEA.—V. On the 
PoLyeLacopHora, or Currons. By E. R. Syxus, F.L.S. 
[Read 2nd May, 1907.] 
I HAvE taken the opportunity of including in this report a series of 
specimens collected by Mr. Crossland in East Africa, owing to the similarity 
of the fauna. 
The collection includes ten species: of these seven are-identified with known 
forms, two are described as new, and one is left for the present unnamed. 
One feature of special interest in this collection is the identification of the 
genus Cryptoplax from the shores of Eastern Africa ; two forms having 
occurred, both of which appear to be specifically identical with those of 
Australia and Kastern Seas. 
ISCHNOCHITON sp. 
Hab. Zanzibar, from a pool in Chuaka Bay, 2-3 fath. 
Two specimens of a very small species of /schnochiton, measuring about 
5 mill. in length. I am unable to identify them, but, owing to their 
diminutive size, it seems wiser for the present to leave them unnamed, until 
either further material or larger specimens be obtained. Colour white, with 
a brown girdle. Shape resembling the usual form of Lepidopleurus. 
Sculpture punctation on the valves. Valve-slits: end-valves about 14 slits, 
median | shit. 
CALLISTOCHITON CROSSLANDI, n. sp. 
Shell oblong, well elevated, not carinated ; pale brownish-white, the girdle 
similar in colour. 
Valves hardly beaked. Lateral areas with two strong riblets, these being 
granulose, and the interstices nearly smooth ; median areas with about twelve 
fairly strong sub-granulose longitudinal riblets, which often break as they 
approach the beak, the interstices smooth. Head-valve with thirteen pec- 
tinated riblets (apparently formed by the splitting of seven).  Tail-valve 
having the mucro median, the posterior slope a trifle concave, with, by splitting, 
fitteen riblets. Interior white, a trifle tinged with brown. Head-valve with 
8, median valves 1, tail-valves 9 slits: teeth finely pectinated. 
Girdle densely covered with well sculptured scales. 
Length about 25, breadth about 15 mill. 
Hab. Shore at Wasin, Hast Africa. 
A single specimen, which I am unable to reconcile with either of the 
two species recorded from the Red Sea. As compared with C. adenensis, 
Smith, it isa larger species, with stronger sculpture and fewer ribs on the 
valves. As compared with the typical form of C. heterodon, Pilsbry, it has 
