194 



Memoirs of the Indian Museum. 



[Vol. V, 



Although both the typical form and the variety have been obtained at a number 

 of localities on the Indian coast, this is the first occasion on which the two have been 

 found together. It is therefore interesting to notice that in the Chilka Lake they are 

 very easily distinguished and that in our long series no single individual intermediate 

 in character was obtained. In specimens of the variety in which the pigmentation is 

 unusually dense, the lateral process of the fifth thoracic somite is occasionally some- 

 what dusky, but never dark enough to cause confusion with the typical form, while 

 the correlated structural differences in the shape of the rostrum and carination of the 

 carapace will also suffice to separate the one from the other. It seems, indeed, not 



by any means improbable that the variety immaculata will 

 ultimately be given specific rank; but, apart from colour, 

 the distinctions are so slight that it is inadvisable to take 

 this course with the information we at present possess. A 

 knowledge of the early stages of the two forms will perhaps 

 afford a useful clue, but the series of larvae obtained in our tow- 

 nettings are all of one type. In view of the great numerical 

 preponderance of the variety immaculata , it seems probable 

 either that they belong to this variety or that the varietal and 

 typical forms are indistinguishable in their early stages. 



Specimens of the variety were obtained in the trawl in 

 many places both in the outer channel and in the main area 

 and were found in the salt-water season, when the water- 

 level was at its lowest, under stones on the shore of Barkuda 

 Id. , living in burrows. The burrows were about half an inch 

 in diameter and were (J or Y-shaped, the distance between 

 the openings being about eight inches. On lifting the stone 

 the whole burrow was sometimes disclosed ; it frequently 

 contained practically no water. The S quitta occupied a 

 slightly widened chamber at the bend of the \J or in the 

 stalk of the Y- Specimens were also observed at the head 

 of Rambha Bay, on mud-flats left bare owing to the action 

 of strong wind. They lay at the mouth of their burrows, 

 which were directed vertically downwards for about 3 inches before turning hori- 

 zontally over a layer of shingle. No individuals with egg-masses were observed. 



Post-larval Forms. 



Our collection contains twenty-seven specimens less than 30 mm. in length which 

 may conveniently be termed post-larval. The series apparently comprises four stages, 

 the lengths of which are approximately 7-5 — 8 - o mm., 1.1-5 — 12 '° mm., 15 5 — i6-o 

 mm. and 25 — 27 mm. There are, however, one or two specimens of intermediate 

 sizes. 



The youngest post-larval stage (text-fig. 1) bears a close resemblance to the adult, 

 but the eyes are proportionately much larger, the rostrum is broader at the base 



Fig. 1. — S quitta scorpio 



var. immaculata, Kemp. 



A post-larval specimen about 

 8 mm. in length. 



