416 CEYLON PEARL OYSTER REPORT. 



The antero-external angle of the merus of the external maxillipeds and the shape 

 of the male abdomen are evidently characters with high variability in this species if 

 Alcook is correct in including both the forms figured by Dana. The present 

 examples agree in combining a merus resembling Dana's fig. 2c with a male abdomen 

 in which the borders are still more sinuous than in his fig. 3b abdominal segment VI. 

 being the one chiefly involved. 



Neptunus (Hellenus) tenuipes (de Ha an, 1835) A. 4, p. 42. 



Locality : Pearl banks, Gulf of Manaar, one specimen. 

 Description: Adult male. C.l. = 16*00. 



Behind the single distal spine of the outer border of the arm is a sub-terminal 

 tubercle marking the position of the second spine of some allied species. 



Neptunus (Lupocycloporus) whitei (A. M.-Edw., 1861) A.4, p. 44. 



Localities : Coral reefs, Gulf of Manaar, two specimens (adult S and adult ? ) ; 

 pearl banks, Gulf of Manaar, one specimen (young ? ) ; off Mutwal Island (young ? ). 



Description: C.l. of adult female = 18 - 00. 



In both the adult specimens (a 8 and a ?) one notes: (1) The cardiac ridge 

 is broken in the middle line so that it takes the form of two low broad tubercles, 

 granulated on their posterior slope ; (2) there is a small granulated protuberance on 

 the post-gastric region ; (3) there is a longitudinal row of granules on the middle line 

 of the carapace ; its anterior commencement is just in front of the break in the 

 anterior gastric ridge, and runs back across the second gastric ridge, to terminate 

 posteriorly between this and the third gastric ridge. 



Neptunus (Achelous) granulatus (H. M.-Edw., 1834) A.4, p. 45. 



Localities: Off Negombo, one specimen; Gulf of Manaar, 17 specimens; off 

 Mutwal Island, one specimen. 



Description : The above specimens include four ovigerous females, five adult 

 females, seven adult males and three young males. C.l. of an ovigerous female =13. 



There is a pearly sheen, much as in N. argentatus, on the crests of abdominal 

 terga II. and III., the terminal spine of the arm, the crest of the outer surface of 

 wrist, and the upper surface of the dactylus. 



The spinule on the hand, in front of the apex of the wrist, is said by Alcock to be 

 blunt. Among the present examples it is sharp, except on the left hand of two and 

 the right hand of three specimens. 



Neptunus (Achelous) dubia, n. sp. Text-fig. 9. 



Localities : Coral reefs, Gulf of Manaar, one specimen ; oft Negombo, one specimen. 



Description .-Adult <? C.l., 13 ; C.b.H-C.L, T31 ; front.b.-i-C.l., 3 '8 5; front. -orb. b. 

 -8-C.L, 0-85; ant.lat.bord. C.-f-C.L, 0-54; post.bord. C.-=-C.l., 0-62 ; post.lat.bord. C. 

 --C.l., 0-58; CLL-S-C.L, 2-00. 



