146 DK- T. DAVIDSON ON RECENT BRACHIOPODA. 



slio-litly indented in front ; liinge-line straight, as long as the hreadth of the shell, forming 

 acute angles at its junction with the labial margins of the valves. Valves vmequally 

 convex. Dorsal valve very gently convex, rather flat, with a shallow longitudinal depres- 

 sion along the middle. Ventral valve convex, with a rather deep mesial sinus, correspond- 

 in"- to the one in the dorsal valve; beak and area sloping backwards, forming an obtuse 

 anc-le with the plane of the dorsal valve. Foramen very large, incomplete, margined 

 anteriorly by the umbo of the dorsal valve, and laterally by rudimentary deltidial plates. 

 Surface of valves traversed with from eight to tAvelve rounded ribs, corresponding in 

 both valves, with interspaces between them of almost equal breadth. Colour pale yellow, 

 with scarlet interspaces ; surface marked with punctuations clearly visible to the eye in 

 a o-ood lia'ht. In the interior of the dorsal valve the apoj)hysary system consists of a 

 bilobed ribbon-shaped lamella, originating at the base of the sockets, which after forming 

 half a circle on each side, adheres to a central prominent submarginal septum, the 

 lamellae forming the loop being also partly confluent with the valve. Proportions 

 variable. Length 3 lines, by a little more than 1 lines in breadth. 



Hah. North-east coast of Jamaica in a depth of 150 fathoms (Barrett). At Guada- 

 loupe in from 200 to 250 fathoms (Crosse). Dredged in 70 fathoms off E,io de Janeiro, 

 Brazil, by the captain of the English steamer ' Norseman,' in lat. 21° J^S' S., long. 40° 3' W. 

 These specimens were obtained attached to corals brought up by the grappling-irons, and 

 sent to me by Mr. E.. Ptathbun. Dredged also by M. de Pourtales west of Tortugas in 

 30 to 43 fathoms ; Sand Key, 80 fathoms ; St. Vincent, 95 fathoms ; Tortugas, 43 

 fathoms ; otf Grenada, 115 fathoms ; Barbados, 100 fathoms ; off Havana, 450 fathoms 

 (Sigsbee), Yucatan Strait, 641 fathoms, ' Blake' Exped. (Dall). 



Obs. This fine species of Clstella approaches most nearly in general appearance to the 

 Cistella cnneata, Eisso, but is a much larger species and possesses, when full-grown, a 

 o-reater numl)er of ribs. In external shape it bears likewise some resemblance to Arglope 

 decollata, from which, however, it can Ije at once distinguished by its two-lobed loop and 

 single submarginal septum. It varies someAvhat also in shape as well as in the number 

 of its ribs, some specimens being as long as wide when quite young. In a letter dated the 

 22nd of March, 1870, Mr. Crosse writes me that in all probability his Argiope antillarum 

 is a synonym of Cistella Barrettiana, but that he considers his C. Schrajnud to be a dis- 

 tinct species. I have also, through the kindness of Mr. Dall, been able to examine the 

 lype of his O. ruhrotincta, and I believe it to be a synonym of C. Barrettiana. Erom 

 Mr. Dall's description it would seem that it is of a pale yellow colour, with brilliant 

 scarlet interspaces, and agrees in shape and character with typical examples of C. 

 Barrettiana. " Septum triangular, extending from the hinge margin to the anterior 

 border of the shell. Most elevated point, forming the apex of the triangle in the middle 

 of the valve, rather bulbous and of a red colour. Anterior slope of the septum to the 

 border of the sheU, straight without nodules ; this part of the septum is thin and even. 

 Posterior slope of the septum irregularly concave, tliick, and nodulous, tapering to a 

 point at the hinge-margin." The size and extent of the transverse plate of the septum 

 varied in different specimens. 



