Barnacles of the Genus Megalasma. 363 



of the posterior cirri have four large pairs and one small pair 

 of anterior spines. In all these characters the specimens 

 agree with Pilsbry's description of the form which he calls 

 Al. helium and which Annandale regards as a local race of 

 his Al. minus. On the other hand, the base of the carina in 

 our specimens, while varying somewhat in shape, is squarely 

 truncate, with the lateral angles more or less produced and 

 acute, and, although without a median tooth, agrees rather 

 better with Pilsbry's figure of the carina of M. minus. 

 Further, a specimen of Al. minus received from the Indian 

 Museum in 1906, and presumably one of the syntypes, has 

 the scutum distinctly less than twice as long as broad, and 

 therefore disposes of the sole character which Annandale 

 retains as distinctive of the species or race. 



Subgenus Glyptelasma, Pilsbry. 



Key to the Species of the Subgenus Glyptelasma *\ 



A. Carina projecting well below scutum, the 



basal margins of the two valves meeting 

 at an angle as seen from the side. 



a. Basal margin of carina, seen from the side, 



as long as that of scutum M.gracile (Hoek), with 



[subsp. yracilius, Pilsbry. 



b. Ba9al margin of carina, seen from the side, 



shorter than that of scutum f. 



a. Carina transversely expanded at the 



base. [No filamentary appendages.] . M. yiyas (Annandale). 



b. Carina not transversely expanded at the 



base. 

 a. Sides of carina widened in lower 



third M. annandalei, Pilsbry. 



j3. Sides of carina widening evenly 



throughout its length. [A pair of 



small filamentary appendages on 



dorsal surface of prosoma near its 



hind margin.] M. pilsfoyi, sp. n. 



B. Carina not projecting far below scutum, the 



basal margins of the two valves in line or 

 forming an even curve as seen from the 

 side. 

 a. Occludent margin of scutum nearly 

 straight, carina with narrow sides, trans- 

 versely expanded at base M. rectum, l'ilsbry. 



* Based on the keys given by Pilsbry (Bull. U.S. Nat. Mus. lx. 1907, 

 p. 83, and Proc. Acad. Nat, Sci. Philadelphia, 1907, p. 415). 



t On this point Pilsbry's description of M. annandalei is at variance 

 with his key and with his figure of that species (Bull. U.S. Nat. Mus. Lx. 

 1907, pp. 83 & 90, pi. vii. fig. 15). 



27* 



