REPORT ON THE BRACHIOPODA. 59 



Cistella cistellula there is but one septum, while in Argiope decollata there are frum 

 three to five. 



Rhynchonella, Fisher. 



Rhynchonella nigricans, var. pixydata, K. B. Watson^ (PL IV. fig. 14). 



Terebratula nigricans, Sow., Proc. Zool. Soc, p. 91, 1846, and Thesaurus ConchyL, p. 342, pi 



Lxxi. figs. 81, 82. 

 WiyncJionella nigricans, Dav., Proc. Zool. Soc, pi. xiv. figs. 30, 31, 1852. 

 Hemithyris nigricans, Dall, Catalogue of the Recent Species of the Class Brachiopoda, Proc. Phil. 



Acad. Nat. Sciences, p. 196, 1873. 



Var. pixydata. — Shell transversely oval, widest anteriorly, tapering posteriorly, 

 wider than long. Dorsal valve uniformly convex to about half its length, when a 

 broad mesial fold, scarcely raised above the general convexity of the valve, occupies the 

 anterior middle of the valve. Ventral valve rather less deep and convex than the 

 opposite one, with a broad, well-defined mesial sinus, commencing at a short distance 

 from the extremity of the beak, and extending to the front. Beak rather small, acute, 

 and incurved ; foramen incomplete, situated under its pointed extremity, laterally mar- 

 gined by narrow deltidial plates ; surface of both valves ornamented by about forty to 

 forty-six small, angular radiating ribs, closely intersected by equidistant squamose con- 

 centric ridges of growth, giving an imbricated appearance to the surface. Colour yellowish- 

 white, sometimes brownish at the beaks. Length 18, width 20, depth 30 mm. 



Habitat. — Six examples were dredged by the Challenger Expedition, south of 

 Kerguelen Island, on February 2, 1874, associated with numerous specimens of Wald- 

 heimia kerguelensis, at Station 150, lat. 50° 4' S., long. 71° 22' E. Dej)th, 150 

 fathoms. Bottom temperature, 1°"8 C. Sea bottom, rock. 



The typical form of the sj^ecies has been often di-edged in about 19 fathoms at 

 Foveaux Straits, five miles ofi" Ruapuke Island, New Zealand. Sea bottom, coral and rock. 



Observations. — Nearly all the specimens from Foveaux Straits, New Zealand, were of 

 a blue, black, or brownish colour, while the six examples dredged by the Challenger 

 Expedition from near Kerguelen Island, were of a light, yellowish-white colour. One, 

 however, showed at the beaks the brown tint of the New Zealand type. The New 

 Zealand shell is also generally more transverse, and comparatively less convex than is the 

 variety from near Kerguelen. The ribs in the latter are likewise more numerous, and 

 smaller. These difi'erences, no doubt, led the Rev. R. Boog Watson to distingui.sh it as a 

 distinct species under the MS. name of p)ixydata, from ttv^, as he thought it like a box 



' By mistake in my Extract of Report on the Brachiopoda dredged by H.M.S. Challenger, read before tlie Eoynl 

 Society on May 8, 1878, this variety was referred to Willemoes-Suhm, but Mr Watson subsequently informed me tliat 

 it was an MS. name of his own. 



