72 



INTRODUCTION. 



Morrisia anomioides (Scacchi, sp,) 



19. Interior of Dorsal I'alve with the Animal. 



20. c, oral processes ; i, foramen. 



Fig. 19. Fig- 20^ Animal furnished with two subspiral or 



sigmoid arms fringed with comparatively large 

 cirri ; these arms originate beside the mouth 

 (as shown in the figure) supported by the 

 crural processes, and after passing forwards 

 and converging in front of the mouth, they 

 again turn outwards, each having the shape 

 of the letter S : external surface smooth and 

 largely punctated. 



Obs. The remarkable arrangement of the oral processes, large foramen, encroaching 

 equally on both valves, and form of the apophysary system, seems to me quite sufficient to 

 distinguish this genus or sub-section from the other genera in the family of Terebratulida. 

 The type was considered by Scacchi and Philippi to belong to Dalman's genus orthis, of 

 which, however, it possesses ?ione of the characters. 



Geol. range. — I am inclined to believe that this httle genus existed in the cretaceous 

 period, possessing several examples of a small shell from the chalk of Gravesend, 

 which so closely resembles the recent type that I can hardly distinguish them even 

 specifically. 



Example : M. anomioides., Scacchi, sp. {recent^ 



Genus — Argiope, Beslongchamps., 1842.^ 



Type — A. decollata, Chem., sp., 1785. Int., PI. VI, figs. 32, 34. 



Anomia and Terebratula, in part of Authors. 



Orthis, of Michelotti, Philippi, Hagenow, ^c, but not Orthis, Bahnan. 



Megathyris, IfOrhigmj, 184/. 



Shell semi-orbicular, quadrate or transversely oval ; valves unequally convex, smooth 

 or variously costated ; ventral or dental valve the deepest, beak produced, with a depressed 

 triangular area ; foramen large, completed by the umbo of smaller valve ; hinge line 

 straight ; valves articulating by means of teeth and sockets. Interior of smaller valve fur- 

 nished with a central septum, and sometimes with one or more lateral septa radiating from 

 beneath the cardinal muscular prominence, and terminating at some distance from the 

 margin in elevated processes ; apophysary system consisting of a distinct loop, originating 

 at the base of the dental sockets and folded into two or more lobes occupying the inter- 

 spaces of the radiating septa to which they adhere on their inner sides ; the labial pro- 

 cesses or arms originate on the sides of the mouth, and diverge right and left parallel 

 with the margin of the shell, but at some little distance from it ; when they arrive 

 at the raised septa they turn inwards, forming one or more lobes on each side of the 



^ Memoirs de la See. Linn, de Normandie, vol. vii, p. 9, 1842. 



