1911.] NATURAL SCIENCES OF PHILADELPHIA. 171 



these discrepant forms the speaker has erected the genera Heteralepas 

 and Paralepas. A true Alepas has been found in the eastern Pacific, 

 A. pacifica Pils. Figures were exhibited of two additional species, 

 obtained by the U. S. Fisheries Steamer "Albatross" in the Philip- 

 pines. 



Among other barnacles commensal on decapod Crustacea, obtained 

 at the Johns Hopkins tropical laboratory at Montego Bay, Jamaica, 

 and submitted by Dr. John Paul Givler, there is a new form of 

 Octolasmis, remarkable for the completely calcified plates. In all 

 other known species of the genus the calcified portions of the plates 

 have been reduced. This is therefore a form retaining archaic or 

 ancestral features. It was found on a spider crab, and may be de- 

 scribed as follows: 



Octolasmis prototypus, n. sp. (figs. 2, 3). — The capitulum is 

 acutely ovate, almost entirely covered by the well-calcified plates, 

 which have the white color and dense texture of the plates of Lepas. 

 The scutum is divided by an arcuate slit into a longer occludent and a 

 shorter, triangular lateral segment. The latter is acute above, rounded 

 at the two basal angles, and nearly as high as wide. Like the tergum, 

 it has faint sculpture of concentric and radiating striae. The tergum 

 is very large, about as long as the carina, and nearly as long as the 

 scutum. The lower end tapers, and extends between scutum and 

 carina; the upper end is truncated, and the scutal margin a little 

 hollowed to receive the apex of the scutum. The carina is but little 

 curved and only shortly forked at the base. It is somewhat separated 

 from the other plates. The peduncle is finely annulated in preserved 

 examples, whitish, and decidedly longer than the capitulum, often 

 H times its length. 



Length of capitulum 3.6, width 2.5 mm.; length of peduncle 3.5 

 to 4 mm. 



The cirri resemble those of 0. forresti. The first pair is very short, 

 widely removed from the second, its rami consisting of 6 and 7 seg- 

 ments, which are densely hairy. The sixth pair has rami of 14 seg- 

 ments, armed comb-like with spines, 9 or 10 pairs on a segment, as 

 figured by Stebbing for 0. forresti (Ann. and Mag. Nat. Hist. (6), XIII, 

 pi. 15, upper right-hand figure). 



Maxillse as in 0. forresti. Mandibles having long spines on the 

 lower side below the lower point. 



This barnacle differs from Paicilasma (Temnasjris) fissum Darwin, 

 and the forms subordinated thereto by Annandale, 1 by the much wider 

 occludent segment of the scutum, especially wide at its tergal extrem- 

 ity, and by the larger tergum. It is also a much smaller barnacle. 

 In P. fissum, Darwin has shown that the cirri have a special arrange- 

 ment of spines, which arise in transverse linear groups at the distal end 

 of each segment, as in Paralepas or Alepas, whereas in Octolasmis 

 prototypus the spines stand along the anterior side of the segments 

 like the teeth of a comb, as in most other barnacles. Barnacles with 



1 Scertnjk af Yidensk. Meddel. fra den naturh. i Kbhvn, 1910, p. 216. 



