88 THE VOYAGE OF H.M.S. CHALLENGER. 



Moseley^ in 1876. It is apparently a deep-sea representative of tlie pelagic Salpidse, 

 and may possibly be fixed to the bottom. Our knowledge of its structure is still very 

 limited, and the embryology and life-history are totally unknown. 



Although in some respects this form does not agree with the definition of the sub- 

 order Hemimyaria given above, still on account of its probable relationship to the 

 Salpidse — and considering the imperfection of our knowledge of Octacnemus — I have 

 thought it best to place it in this sub-order, at least until we know more about it, 

 rather than to form an additional group for its reception. 



Octacnemus, Moseley. 

 Odacncmus, Moseley, Trans. Linn. Soc. Lond., scr. 2 (ZooL), vol. i. p. 287, 1876. 



Body flattened antero-posteriorly (?), probably attached by the posterior end. 

 ]\Iargins prolonged to form eight conical processes. 



Test gelatinous, thin, transparent. 



Mantle slight. Musculature in the form of narrow muscle bands, which are 

 mainly confined to the conical processes. 



Branchial Sac with its length directed dorso-ventrally, and having merely im- 

 perforate pits in its walls, and no direct connection with the peribranchial 

 cavity. 



Dorsal Lamina unrepresented. 



Alimentary Canal coiled up along with the reproductive organs to form a 

 visceral mass, placed at the dorsal edge of the posterior end of the body. 



Reproductive Organs hermaphrodite. 



Further characteristics and remarks upon the structure and afiinities of the genus 

 will be found under the species described below. 



Whether the two specimens in the collection represent distinct species or not, I 

 cannot determine. They differ in some respects, but are so imperfect, that I do not 

 feel justified in founding a second species. 



Octacnemus hythius, Moseley (PI. X. figs. 1-18). 



Octacnemus li/thius, Moseley, Trans. Linn. Soc. Lond., scr. 2 (Zool.), vol. i. p. 287, 187C. 



Tills .species was formed by Professor Moseley in 1876 for the reception of a 

 specimen obtained on March 1, 1875; Station 218; South Pacific; lat. 2° 33' 0" S., 



' Ou two new Forms of Deip-sea AsciJians, obtained during the Voyaj^e of H.M.S. " Challenger," Trans. Linn. 

 Soc. Lond., ser. 2 (Zool.), vol. i. p. 2S7, 1876. 



