1909.] N. ANNANDAI.E : The Indian Cirripedia Pedunculata. 87 



is narrower than the carinal ; umbo at the rostral angle. Tergum triangular 

 or nearly so, absent in one species. Carina forked at the base or expanded 

 into a more or less well-developed transverse disk, not expanded vertically ; 

 its apex reaching or extending for a short distance between the terga above ; 

 its umbo basal. Peduncle well developed, naked, or bearing small chiti- 

 nous plates. Filamentous appendages absent; caudal appendages consist- 

 ing of a single joint, cylindrical or laterally compressed, not claw-shaped, 

 bearing at the tip a pencil of fine hairs. Mandibles with four or five (rarely 

 six) teeth, inclined to be variable ; maxillœ with the free edge straight or 

 broken by a single incisure, not step-formed. 



This genus is easily distinguished from Lepas by the structure of its anal append- 

 ages and maxillae ; it fades almost imperceptibly into Dichelaspis , from which it is 

 only distinguished by the perfect development of its valves. From Megalasma, Hoek, 

 it is distinguished by the shape of the carina at the base — a character which is perhaps 

 of no more than subgeneric value. 



Strictly speaking, as Darwin was well aware and as Pilsbry has recently pointed 

 out, the name of the genus should be Trilasmis, for a species was described under that 

 name by Hinds in 1844. The species {T. eburnea), however, was an aberrant one, 

 and the name has so long been obsolete that to revive it would only cause confu- 

 sion. I have therefore neglected to follow the strict laws of priority in this 

 instance, retaining Hinds's name merely as that of a subgenus. 



Four ' Indian species of Pœcilasma are known ; they may be distinguished as 

 follows : — ■ 



Key to the Indian species of Pœcilasma. 



I. Valves complete ; scutal margin of tergum straight. 



A. Carina narrow, truncated at the base . . . . P. kœmpfevi. 



II. Scutum divided vertically ; scutal margin of tergum straight. 

 A. Tergum with the occludent and apical angles more or 



less rounded and the carinal angle truncate . . . . P. fissum. 



III. Scutum divided vertically ; tergum present, its scutal margin 

 excavated to correspond with the tip of the occludent margin 

 of the scutum. 

 A. Valves closely approximate ; occludent margin of the 



scutum strongly curved . . . . . . P. minutum. 



IV. Tergum absent ; scutum inflated. 



A. Scutum with a strong internal tooth, not divided, but 



possessing a distinct vertical suture . . . . P. eburneum. 



1 The specimens identified as representing P. gracile, Hoek {Rec. Ind. Mus., vol. i, p. 81 (1907), 

 are young examples of Megalasma minus, which, at an early stage, closely resembles P. gracile exter- 

 nally. 



