354 CEYLON PEARL OYSTER REPORT. 



specimen (6) ; pearl banks, Gulf of Manaar, four specimens (c, <7, e, f) ; Galle, one 

 specimen (g). 

 Description : 



(a). (A). (c). (<l) young ?. (e) young ?. (/) young?. (</) adult <J. 



0.1. . . 1275 1275 13-50 21 '00 22'00 30'00 37 '50 



C.b. -s-C.1. 1-25 1-25 1-27 1'32 1'38 1-44 



Specimens (f) young female and (g) male answer well to ALCOCK'S description. In 

 the young forms (a to e) the endostome septum is deeply concave anteriorly, and this 

 is to be noted since the strongly convex character of this region is one of three 

 characters by which ALCOCK distinguishes adults of C. philargins from those of 

 C. lophos. A parasitic Sacculina is attached to the abdomen of (g) male ventrally, in 

 the joint between somite VI. and the telson it has not produced any obvious change 

 of the secondary sexual characters. 



Calappa gallus (HERBST), 1803 A. 2, p. 146. 



Localities: Series (A) Mutwal Island, Station LXVL, one specimen; south of 

 Modragam, one specimen ; Chilaw Paar, Station LXIX. , one specimen ; coral reefs, 

 Gulf of Manaar, two specimens ; pearl banks, Gulf of Manaar, six specimens. 

 Series (B) Coral- reefs, Gulf of Manaar, two specimens ; pearl banks, Gulf of Manaar, 

 eleven specimens ; Gulf of Manaar and Palk Straits, three specimens ; off Kaltura, 

 Station XLIIL, 22 fathoms, one specimen; west of Periya Paar, Station LXIIL, 17 

 to 24 fathoms, two specimens ; ten miles north of Cheval, one specimen. 



The specimens fall into two morphological series (A and B) which differ in certain 

 particulars. Members of both series are often obtained from the same locality. The 

 figures of HERBST and of KLUNZINGER (K., pi. ii., fig. 14) answer in general to (A), 

 and that of BRITTO CAPELLO to (B). The differences are as follows : 



Rostrum. (A) Anterior border blunt and not at all or but little emarginate ; 

 indications of two blunt longitudinal ridges on ventral surface. 



(B) General appearance more elegant ; anterior border sharper and more definitely 

 emarginate ; longitudinal ridges of under surface are fairly sharp compared with (A). 

 Teeth of hepatic region of antero-lateral border small in (A) ; obsolescent in (B). 

 Tubercles of Carapace. (A) The rounded tubercles tend to be rough and fairly 

 prominent ; the beaded squamiform tubercles occupy a good deal of posterior half of 

 carapace, and they form lines which curve forward on the clypeiform expansions. 



(B) Rounded tubercles smoother and more flattened ; the beaded tubercles occupy a 

 more limited region, and form lines which are approximately straight on the clypeiform 

 expansions. 



Hepatic region strongly concave in (A) ; slightly concave in (B). 

 Hair. (A) Posterior border of carapace and of clypeiform expansions sparsely 

 fringed ; three characteristic tufts placed transversely on abdominal tergum II. ; a 



