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XIV. On two new Forms of Deep-sea Ascidians, obtained during the Voyage of 

 R.M.S. ' Challenger: By H. N. Moseley, M.A., F.R.S., Fellow of Exeter College, 

 Oxford. {Communicated by Dr. J. Murie, F.L.S.) 



(Plate XLIV.) 

 Bead December 21st, 1876. 



X HE two Ascidians herewith described and delineated are most unusual and aberrant 

 in several particulars and quite new to science. 



The first form was obtained from the great depth of 2900 fathoms. I propose to 

 name it Uypobythius calycodes, in allusion to its occurrence at a vast depth and its cup- 

 like form. It was unfortunately imperfect when obtained. It is remarkable for 

 having a series of cartilaginous plates developed in its otherwise rather soft and 

 yielding test, which plates are arranged in symmetrical patterns, as will be seen by the 

 figures. 



The other form, which I propose to name Octacnemus bythius, is most remarkable, on 

 account of its stellate eight-rayed form, and abnormal in the details of its structure. It 

 was obtained from 1070 fathoms. It appears to be entirely without near allies in the 

 group of Ascidians. The gill-sac is flattened out so as to be nearly horizontal, and 

 there is no gill-network. Peculiar developments of the muscular tunic are prolonged 

 into the eight curious conical protuberances of the test. The principal viscera are con- 

 tracted within a small rounded mass or nucleus, as in Salpa. 



As only a single specimen of each of the forms was dredged by H.M.S. ' Challenger,' 

 the specimens themselves are, I presume, unique ; and since they are highly interesting 

 in many respects, are well worthy of the Linnean Society's notice. 



I. Hypobythitts calycodes, gen. et sp. nov. (Plate XLIV. figs. 1-6.) 

 On July 5th, 1875, the trawl was used in 2900 fathoms in the North Pacific Ocean, 

 lat. 37° 41' N., long. 177° 04' W. The bottom consisted of a red clay with numerous 

 concretions of peroxide of manganese. A gigantic Hydroid, a Monocaulus * seven feet in 

 the length of its hydrocaulus, fragments of BZyalonema, a Holothurian, and a few other 

 animals were obtained, and with them the Ascidian now to be described in detail. The 

 specimen was considerably lacerated, but almost all its essential structures were pre- 

 served. The animal has the form of an inverted cone, compressed laterally so as to have 

 an oval transverse section. Prom the apex of the inverted cone is continued a cylindrical 

 stem, which is enlarged towards its inferior extremity (PI. XLIV. fig. 1). That side 

 of the animal on which the ganglion lies will be denoted the dorsal. The animal is 

 viewed from the ventral surface in fig. 1. The test is hyaline and extremely transparent. 



* See a letter by G. J. Allman, P.E.S., in ' Nature,' vol. xii. Oct. 28, 1875. 

 SECOND SERIES. — ZOOLOGY, VOL. I. 2 Q 



