418 CEYLON PEARL OYSTER REPORT. 



Description: The above include one ovigerous female, six adult non-ovigerous 

 females, uiue young females, five adult males, and two young males. The specimens 

 from " Coral reefs, Gulf of Manaar," are larger than those from the other localities. 



Neptunus convexus is not definitely included in the Indian fauna by Alcock (A. 4, 

 p. 32). He suggests that its affinities are with the sub-genus Neptunus. It seems 

 advisable to keep it apart, however, as the single representative of Pontus, a sub- 

 genus re-defined by dr Man (' Abh. Senckenb. Ges.,' xxv., pt. iii., p. 643, pi. xxi., 

 fig. 27, 1902). 



Charybdis (Goniosoma) natator (Herbst, 1794) A.4, p. Gl. 



Localities : Off Mutwal Island, two specimens ; pearl banks, Gulf of Manaar, 

 thirteen specimens. 



Description : The above include four females and eleven males, all young. 



Charybdis (Goniosoma) orientalis, Dana, 1852 A.4, p. 63. 



Localities : Coral reefs, Gulf of Manaar, five specimens ; pearl banks, Gulf of 

 Manaar, fifteen specimens ; south of Galle, one specimen ; off Mutwal Island, one 

 specimen. 



Description : C.l. of ovigerous female = 9 - 50. 



Charybdis (Goniohellenus) ornata, A. M.-Edw., 1861 A.4, p. 64. 



Locality : Coral reef, Galle, one specimen. 



Description: The specimen is a male, C.l. 975. 



The last of the antero-lateral teeth is a little larger than the others instead of 

 smaller as in Alcock's description. A parasitic Sacculina is attached to the 

 abdomen. On comparing the crab with one of similar size in the British Museum 

 (ref. 73.28) I find that this has had little effect upon the form of the abdomen, but 

 that the copulatory appendages are sensibly less developed. 



Thalamita prymna (Herbst), var. crenata (= T. crenata, Latr.) A.4, p. 76. 



Locality : Trincomalee, three male specimens. 



Description :- - 



C.l 29-00 38-00 41-00 



Ob. ^ C.l. ... 1-47 1-49 1-50 



The high variability in size is to be noted, as all three are possibly adult. 



Thalamita prymna (Herbst), var. annectans, nov. 



Locality : Trincomalee, two specimens. 



Description: One is a small, but quite probably adult, male, C.l. = 16 '00. 



The following are its most interesting characters for systematic purposes : (I) The 

 fourth tooth of the antero-lateral margin of the carapace is rudimentary ; (2) the 

 ridge on the basal joint of the antenna bears spines; (3) the four middle lobes of the 



