444 Mr. T. Davidson on the Brachiopoda. 



of the calcareous processes in Thecidium with the corresponding 

 portions in the other genera of the family Terebratulida. 



I limit myself at the present moment to the simple announce- 

 ment of this point, not having as yet sufficiently studied the 

 question, but which I shortly intend to do more fully, when 

 entering upon the internal details of the apophysary system of 

 the Morrisia Davidsoni in a paper now in hand, and which also 

 relates to other new Brachiopoda to be published in the Memoirs 

 of the Linnsean Society of Normandy. 



8. Description of a new species of recent Rhynchonella. 

 By S. P. Woodward, Esq., F.G.S. 



Rhynchonella Grayi, n. sp. PI. X. fig. 16. 



Shell light horn-colour, dull, trigonal, depressed; sides 

 rounded ; front truncated ; beak small, acute ; valves smooth, 

 obscurely marked by lines of growth, and strongly plaited near 

 the margin with four central plaits and three or four on each 

 side, the furrows obscui-ely striated ; margins of the valves sinu- 

 ated in front and strongly toothed ; foramen minute, completely 

 tubular. Long. 15, lat. 13, alt. 8 mill. 



This interesting and at present unique shell was sent with 

 other natural-history objects from the Feejee Islands by J. 

 M'Gillivray, Esq., Naturalist to the Surveying Expedition under 

 Capt. Denham of H.M.S. Herald. No particulars as to its 

 habitat have been received; it differs from both the known 

 species of living Rhynchonella (figs. 17 & 18) in its lightness of 

 colour, the others being black ; in the plication of the borders of 

 its valves, which reminds us of the fossil Rh. subplicata (Man- 

 tell) and Rh. lineolata, Phil. ; and especially it differs in having 

 a foramen quite separate from the hinge-line by the development 

 and union of the two elements of the deltidium, in this respect 

 agreeing with the ordinary adult condition of the fossil Rhyn- 

 chonellce. Were it not for the remains of the pedicle and traces 

 of the mantle in its interior, we might have taken it for a plio- 

 cene fossil, being exactly similar in its colour and dull translu- 

 cency to the specimens of Rh. psittacea found in the Crag at 

 Norwich. The muscular impressions are like those of the type, 

 and the interior has traces of unsymmetrical vascular markings. 



If only the recent species were known, the genus Rhynchonella 

 might be thought a remarkable exception to the law of continuity 

 of generic areas, but like many other widely scattered types, its 

 distribution is rendered intelligible by the knowledge of the 

 existence of so many fossil forms in the wide intervals between 

 the localities of the living species. 



