366 CEYLON PEARL OYSTER REPORT. 



Arcania quinquespinosa, Alcock and Anderson, 1894 A.2, p. 266. 



Locality : West of Periya Paar, 17 to 24 fathoms, one specimen. 



Description : Adult female, CI. = 11 "00 (includes frontal lobes, but not posterior 

 spine); Cb. (without spines) CI. = 1'05; lateral spine 1. -J-Cl. = 3*41 ; Ch.L -J-C.1. 

 = 2*23 ; F.l. -7-H.l. = 1'50. The pair of postero-lateral granules is present. 



Arcania erinaceus (Fabricius), 1787 A.2, p. 268. 



Localities : Pearl banks, Gulf of Manaar, two specimens (a, c) ; coral reefs, Gulf 

 of Manaar, one specimen (6). 



Description (measurements as in A. quinquespinosa) : 



(a) young ? . (b) ad. S ('') ad- ? 



G.l 13-25 18-50 18-75 



Cb. -j-C.l 0-87 0-84 0-88 



CLL-fCJ 1-55 1-57 1-49 



F.l.-f-H.l 073 059 0-61 



A difference between the adult male and the adult female above is the presence in 

 the latter of a median longitudinal line of hair on the ischium of the external 

 maxilliped. 



Arcania tuberculata, Bell, 1855 A.2, p. 268. 

 Locality: Pearl banks, Gulf of Manaar, two specimens (a, b). 

 Description: 0.1. O.b.-5-C.l. GE.1.-S-0.1. F.L-j-H.1. 



(a) ovigerous ? . . . 9"50 0-89 1*18 077 



(b) ovigerous ? . . . 10'25 0-88 T17 0'85 



Arcania pulcherrima, Haswell, 1879 A.2, p. 269. 



Localities : Trincomalee, one specimen (a) ; coral reefs, Gulf of Manaar, one 

 specimen (6). 



Description: 0.1. C.b.-s-C.l. Gh.l.-s-C.L F.I.h-H.1. 



(a) young 6 .... 8"00 1'09 2-06 0"82 



(&) ovigerous ? . . . 10-75 1'09 2'16 077 



There are in both specimens 14 tubercles on the dorsal surface of the carapace in 

 addition to the 10 marginal prominences. 



Ixa cylindrus (Fabricius), 1787 A.2, p. 271. 



Localities : Aripu Reef, one specimen () ; pearl banks, Gulf of Manaar, one 

 specimen (b). 



Description (lateral spines included in Cb.) : (a) ad. (J. (b) ad. non-ov. ? . 



CI 14-50 1675 



Gb.-rCl 2-83 2-88 



