ii6 



Memoirs of the Indian Museum. 



[Vol.. II, 



Dichelaspis grayii is common on the sea-snakes of Indian seas and I have been 

 able to examine over 800 specimens in all. This series exhibits every gradation 

 between the typical form and D. pellucida^ of which Darwin said, '' I should not be 

 much surprised if the present form were to turn out to be a mere variety " [of D. 

 grayii^ 



The variety described above as var. pernuda is, however, a most remarkable 

 form. I have found it in considerable numbers on three sea-snakes from different 

 localities, always by itself so far as other cirripedes were concerned. A careful 

 comparison of cirri, mouth parts, etc., with those of specimens of the typical form 

 of the species shows no constant difference, while Darwin's description of these 

 organs fits more exactly to one specimen of the variety than to any individual of the 

 typical form I have dissected. The long anal appendages, which in some specimens 

 of the typical form are distinctly segmented, are particularly characteristic of the 



Fig. g.— Mandible and maxilla of D. grayii var. pernuda, x 240. 



Species, although their exact relative length is variable, while the arrangement of the 

 armature and ornamentation of the mouth parts also affords a sufficient means of 

 diagnosis. 



The new variety affords another link between three subfamilies of the Lepadidœ 

 {i.e., the lyCpadinse, the Pœcilasmatinse and the Alepadinse). The nakedness of the 

 capitulum and its lack of a muscular layer may be only an adaptive resemblance to 

 the genus Alepas, from which the well-developed cirri at once distinguish it. The 

 absence of a muscular layer and of lateral appendages separates it from H eter alepas, 

 to which, however, it exhibits a certain resemblance as regards the anal appendages 

 and mouth parts. Both the variety and the typical form of the species, moreover, 

 differ as regards these structures from most other species of Dichelaspis ; but it is 

 impossible to separate them from that genus. 



