390 CEYLON PEARL OYSTER REPORT. 



Description: (a) young ?. (ft) young ?. (c) adult ?. ((/) young <$. () young <J. (/) adult g. 

 C.l. . . . 7-00 13-00 15-00 8-50 9'25 13-25 



Ch.l.-7-C.l. . 2-75 2-62 277 271 2"65 2'57 



The above series present but little variation among themselves. They come under 

 var. planifrons, with some approach also to var. granulosus. Thus adult female (c) 

 bears considerable resemblance to Miers' specimen of var. planifrons in the British 

 Museum, excepting that the spines of the posterior border of the hand are neither so 

 flattened nor so broad, i.e., more as in var. granulosus, and in the same example the 

 apex of the rostrum is a further point of resemblance to the latter variety. 



The number of spines on the outer border of the hand is fairly constant, that of 

 the teeth of the inner border more variable. Thus in all the specimens there are on 

 the outer border of the hand six large smooth spines and four smaller alternating 

 ones (the most distal of the alternating spines is in (b) larger than in the others, and 

 in (f) it is almost the size of the larger ones) ; the inner border bears from eleven to 

 thirteen teeth. 



Lambrus (Aulacolambrus) curvispinis, Miers, 1879 A.l, p. 274. 



Localities : Galle, one specimen (adult ? ) ; Trincomalee, one specimen (ovigerous ? ). 



Description: Adult? C.l. = 21-00 ; Chl-f- C.l. = 3-07. 



Ovigerous ? . . . . C.l. = 24-00; Ch.l.-s-C.l. = 3-15. 



Lambrus (Parthenolambrus) calappoides (Adams and White), 1847 A.l, p. 275. 



Localities : Coral reefs, Gulf of Manaar, nine specimens (a to i) ; Trincomalee, one 

 specimen (j). 



Description : 



()yg-?-( J )yg- ? ()yg-?- (<Z)ad.?. 

 C.l. . . . 9-50 14-50 15-75 19"25 

 Ch.l.-rC.l. . 1-84 1-84 



The present examples show a good deal of variation about two centres ; the two 

 groups I call var. alcocki (corresponding more or less with Alcock's description of 

 L. calappoides) and var. confragosus (= L. confragosus, Calm an). 



I have seen the " type "-specimens of L. confragosus in the British Museum, and 

 find that with the aid of the present forms and of the British Museum examples of 

 L. calappoides I can arrange a transitional series which unites the two forms named. 



Differences between the two varieties are : (1) The post-ocular notch is well 

 indicated in var. confragosus ; absent in var. calappoides. (2) The lateral hepatic 

 region is prominent, dentiform and compressed in var. confragosus ; little prominent 

 and rounded in var. calappoides. (3) The post-hepatic notch is well indicated in var. 

 confragosus ; slightly so in var. calappoides. (4) The median dorsal spines are 

 prominent and pointed backward in var. confragosus ; in var. calappoides they are 

 represented by inconspicuous tubercles. (5) The tubercles of the carapace are 



