370 J. WILFRID JACKSON ON 
The very wide range of this species is, in all probability, due to larval trans- 
portation, as the larvee are known to live in a free and floating condition for nearly 
a month, and have been taken in a drag-net not far from land (ScHucHERT, 1911). 
Hemithyris sp. (PI. IL. fig. 14.) 
Hab.—Station 417; lat. 71° 22’8., long. 16° 34’ W. (off Coats Land, Antarctica). 
Depth, 1410 fathoms. March 18, 1904. Sea bottom, blue mud and stones. Tem- 
perature 29°°9 F. 
Obs.—Some fragmentary remains of a probable new Rhynchonelloid were met with 
at the above station. These consist of hinge portions only of one ventral and two 
dorsal valves, but are, unfortunately, too small and imperfect for accurate specific 
description. 
The material at my disposal appears to belong to a small trigonal form possessing 
a thin, translucent test. The colour is a yellowish-brown, and the outer surface smooth 
with very faint growth lines. 
The ventral valve possesses dental plates, as in the type species Henuthyris. 
psittacea, and from the evidence of the fragment the beak appears to be somewhat 
produced, and to possess a moderately large foramen. 
The dorsal valve exhibits a short, feeble, median septum separating well-marked 
muscular impressions. There is no cardinal process. Hinge plate divided and 
consisting of two short, flattened, curved lamellee, which are widely divergent. 
Shell-mosaic similar in character to but larger in size than that of R. cornea figured 
by BLocuMann (1908; pl. xxxvii. fig. 16). 
Fig. 14 (Pl Il.) in the present report is taken from a fairly well-preserved 
fragment. 
The above description, of course, applies only to the posterior portion; the anterior 
end of the shell is quite unknown, hence one cannot say if the species is plicated 
or not. 
Two new species of Rhynchonella (A. racovitze and FR. gerlacher), and several 
indefinite forms too imperfect for identification, have been described from the Western 
Antarctic by Jousin (1901), but these all come from a less depth than the Coats Land 
form. This latter may, however, be intimately related with one or other of these 
forms, but owing to the paucity of material in both cases a decision on this point is for 
the present out of the question. 
It is most, unfortunate that the fragments of the Coats Land example are so small 
and indefinite, as this prevents a comparison being made, not only with the above- 
mentioned recent forms, but also with the fossil examples of HMenuthyris recently 
described by Buckman (1910) from Antarctica (Swedish Expedition), especially 
H. antarctica, Buck., from the Pleistocene beds of Cockburn Island, off Graham Land, 
to which species the Coats Land form presents some points of resemblance. 
