362 Dr. W. T. Caiman on 



Pilsbry's subgenus Glyptelasma, the characters of which I 

 have already discussed *. It is distinguished from Mega- 

 lasma, s. str., by the fact that the basal margin of the scutum 

 forms a distinct angle with the chord of the occludent margin, 

 whereas in Megalasma the two are in line or nearly so. 

 In the species referred to Megalasma also the valves are 

 more strongly sculptured than they are in the species of the 

 subgenus Glyptelasma. 



Annandale's Pwcilasma {Glyptelasma*) gig as is in gome 

 respects the least typical species of the genus. The expanded 

 sides of the carina are less marked in external view than 

 in the other species, and Annandale was so far justified in 

 regarding it as forming a transition to the genus Pascilasma. 



As I have already pointed out, there is great diversity as 

 regards the so-called " filamentary appendages " in the species 

 referred to Glyptelasma, and the specific differences to be 

 observed in the disposition of these appendages are in some 

 cases more striking than those exhibited by the valves of the 

 shell. In many species, however, these structures have not 

 yet been examined. 



Genus Megalasma, Hoek. 

 Subgenus Megalasma, s. str. 



Megalasma (Megalasma) minus, Annandale. 



Megalasma striatum, subsp. minus, Annandale, Ann. & Mag. Nat. 



Hist. (7) xvii. 1906, p. 399; id. Illustr. Zool. 'Investigator,' Crust. 



Entoni. pi. i. tig. 8 (1907). 

 Ta'dhisma helium, Pilsbry, Bull. Bur. Fisheries Washington, xxvi. 



1907, p. 183, pi. iv. tig. 6. 

 Megalasma minus and M. helium, Pilsbry, Proc. Acad. Nat. Sci. 



Philadelphia, lix. 1907, p. 409, figs. 

 JUct/alas/iui li/watum,B.oe\i, ' Siboga ' Exp., Cirripedia Peduuculata, 



1907, p. 31, pi. iv. tigs. 1-8. 

 Megalasma minus, Bace I. and Bace II. (71/. helium), Annandale, Mem. 



Indian Mus. ii. 1909, p. 96. 



Locality.— Lat. 6° 58' S., long. 39°16'E. (near Zanzibar), 

 270 fath. C./iS. 'Sheiard Osborn/ About 20 specimens. 



Remarks. -r-The specimens are of relatively large size (up 

 to 14 mm. capitular length) ; the scutum is less than twice 

 as long as wide ; the lateral border of the peduncular fora- 

 men, seen from the side, is straight; the proximal angle of 

 the mandible is very distinctly forked ; the middle segments 



* Ann. & Mag. Nat. Hist. (9) i. p. 407 (1918). 



