Mr. T. Davidson on the Brachiopoda. 448 



7. On a new species of Morrisia. 

 By Eugene Eudes Deslongchamps. 



Morrisia Davidsoni, E. Desh. PI. X. figs. 20, 20 a, b, c, d. 



Shell thin, subpellucid, of a light yellowish colour, varying in 

 shape, but generally transversely oval and irregular. Structure 

 largely punctate, exterior surface covered with small spinose 

 asperities, which are particularly visible near the edges of the 

 shell, and marked by lines of growth. Larger or ventral valve 

 convex, with a straight hinge-line and narrow area ; deltidium very 

 small, edging only the very small portion of the foramen exist- 

 ing in this valve. Smaller or dorsal valve almost flat, assuming 

 the shape of the objects to which it lies in close contiguity, and 

 deeply notched at the umbo by a large circular aperture, which 

 constitutes by far the greatest portion of the foramen. Valves 

 articulating by means of minute teeth and sockets. Apo- 

 physary system consisting of two lamellse originating at the base 

 of the sockets, and united to a small elevated process or septum 

 which arises from near the centre of the valve. Length 3, 

 width 5 lines. 



Hab. Found adhering to large specimens of the Caryophyllia 

 ramea, probably derived from the coral fisheries near Tunis. 



Obs. This species is at once distinguished from the Morrisia 

 anomioides of Scacchi (fig. 19) by its larger dimensions, trans- 

 versely oval shape, and the flatness of its dorsal valve, as well as 

 by the minute spinose asperities which cover its surface ; the fora- 

 men in the present form also encroaches to a much larger extent 

 on the dorsal valve than on the ventral one, or than is the case in 

 Prof. Scacchi^s species, which is, besides, almost circular, smooth, 

 with both valves moderately convex. In M. Davidsoni the 

 smaller valve is also at times very irregular, occasioned by the 

 shortness of the peduncle, which forces the shell to lie in close 

 contiguity with the objects to which it is moored, and take more 

 or less the impress of their irregularities. 



Prom a superficial examination of the animal in its dried-up 

 condition, my father and myself were enabled to convince our- 

 selves, that in the species under description the oral arms seem 

 to be connected with the apophysary system by a kind of very 

 delicate calcareous network, reminding one of the descending 

 apparatus of Thecidium, which in some species is formed in its 

 upper portions by a calcareous network freely suspended above 

 the visceral cavity. MM. 0. Schmidt and Suess have already 

 recognized the tendency to a disposition somewhat similar in 

 the subgenus Terehratulina. This important fact will, in all 

 probability, at a future period help to identify the difierent parts 



