CALClfEKOTJS SANDSTONE OF PIFE. 585 



Trochfs seekilimba, Phillips, Geol. Yorks. pi. xv. f. 30. 



A small elongately trochiform shell occurs with the other uni- 

 valves in the limestone east of Eanderstone Castle. It is one fifth 

 of an inch in length, and one eighth wide, with from six to seven 

 gradually increasing and strongly tuberculated whorls ; and it seems 

 to be identical with Trochus semlimha, Phillips, so far as can be 

 judged from the figure of that species in the ' Geology of Yorkshire.' 



AvicuLA EECTA, M'Coy, Syn. Carb. Foss. Ireland, p. 84, pi. xiii. 

 f. 24. 

 Specimens of an Aviculoid shell having much the character of 

 this species occur in various beds. They are rather longer com- 

 pared with the width than M'Coy's figures, but they have the sur- 

 face ornamented with the same regular raised lines of growth as his 

 species. 



Ctpeicaedia bicosta, sp. nov. 



This shell has only occurred in the limestone to the east of 

 Eanderstone Castle, where it is pretty common. 



It is small, thick-shelled, subquadrate in outline, and has two ribs 

 or keels running from the umbo diagonally to the posterior portion 

 of the valve. It is ^ of an inch long and ^ of an inch wide. 



Myalina modiolifoemis, Brown. 



Avicula modioliformis, Brown, Possil Conchology, pi. Ixvi. f. 19. 



Myalina communis, Kirkby, MS. 



I am not sure that the Myalina of the shell-beds of the east of 

 Fife is the same as the Water-of-Leith shell found at Woodhall, and 

 described by Capt. Brown as Avicula modioliformis ; but I think 

 it possible that it is so, and adopt this specific name rather than risk 

 the creation of a synonym. 



The Fifeshire shell, however, appears to be distinct from M. crassa, 

 with which Mr. Etheridge has identified the Woodhall species, for 

 the following reasons : — its relatively larger and more gibbous um- 

 bones ; its more delicately striated cartilage -area ; its regular, wide- 

 apart, imbricating lines of growth ; and its possession of an anterior 

 tooth and socket in each value. 



It is also a smaller shell, rarely exceeding an inch and half in 

 diagonal length. It is always found best developed in the lime- 

 stone and calcareous ironstones ; and it is only in such specimens that 

 the peculiarities of its hingement are to be seen. In the shales it is 

 often very thin-shelled, with little or no cartilage- area, and might 

 easily be mistaken for a species of Anihracomya were it not for its 

 characteristic lines of growth. 



At one or two localities a larger Myalina is found, and it appears 

 to come nearer M. crassa. The best examples of this form that I 

 have seen occur at the " Pans " west of Crail, in a limestone that 

 represents another outcrop of Zone 10 of the Pittenweem and An- 

 struther section. It is nearly three inches in length, and has the 

 more terminal upibones and strong cartilage-striae of M. crassa, 



