372 MR. W. F, LANCHESTER ON THE [DeC. 2, 



longish, stiff hairs, the apex with the usual bundle of short 

 bristles. 



This species, which Mr. F. F. Laidlaw kindly brought to my 

 notice on an Enhydris which he was examining, is possibly 

 identical with one of which Darwin had only a single young and 

 imperfect specimen, taken off Borneo, from the skin of a sea- 

 snake. It agrees in the presence of the "two or three very 

 distinct ridges on each side of the midrib " internally ; but I have 

 been unable to satisfy myself, in these small specimens, of the 

 existence of any pores in the parietes, so that an identification 

 with Darwin's form must remain a matter of doubt. 



It is clearly marked off from the other two species described by 

 Darwin — {a) from P. hissexlohata by the subequality of the rami 

 of the 1st cirrus, and (6) from P. decorata by the very moderate 

 convexity of the basis. Moreover, to judge from Darwin's 

 figures, the shell and opercular valves would seem to be consider- 

 ably thinner in our species, 



XIII. Genus Ibla Leach. 



26. Ibla quadrivalvis Cuvier. 



Anatifa quadrivalvis Cuv. Mem. pour servir . . . MoUusq. 

 figs. 15-16 (1817). 



Ibla quadrivalvis Darwin, ' Lepadidse,' p. 203, pi. iv. fig. 9 

 (1851). 



Log. Pulau Bidan, Penang. Numerous specimens. 



XIY. Genus Lepas Linn. 



27. Lepas anserifera Linn. 



Lepas anserif era JArm. Syst. ISTat. (1767); Darwin, 'Lepadidse,' 

 p. 81, pi. i. fig. 4 (1851). 



Log. Patani. Two specimens. 



XV. Genus Dichelaspis Gray. 



The following key to the species of this genus is partly based 

 on that given by Hoek in the Report on the Oirripedia col- 

 lected by the 'Challenger,' and amplified by Stebbing in the 

 'Annals and Maga,zine of Natural History,' (6) xv. p. 21 (1895); 

 but I have modified it somewhat in Group B, owing to the 

 relatively larger number, namely eight, of new species which now 

 have to be included in that group, 



A. Carin£|, terminating in a disk. 



Basal segment of scutum narrower than occludent. 

 Tei'gum axe-shaped. 



Edgecrenate D. grayiiD&Y^m. 



Edge smooth B. peliucidaDa.vvim. 



Basal segment twice as broad as occludent D. warwickii Darwin. 



Basal segment thrice as broad as occludent. 



Tergum narrowing anteriorly D. aM%M« Stebbing. 



lergum widening anteriorly D.hoeki Stebbing. 



