1867.] Appendix. 219 



unibo-niargiiial diameter being the longest. The shell was at first 

 very gibbose, but after the second line of growth it is much less so. 

 Four sunken lines of growth are well marked. Ears small and trans- 

 versely striated. Shell nearly equilateral, beak prominent. 



The cast shows two deep pits, corresponding on the inside of the 

 shell to two tubercles. These pits are more than half way clown 

 the valve. The cast is covered with shallow irregular fossae which 

 correspond to small bosses inside the shell, and are probably due to the 

 presence of pearly matter. There are traces of an epithelium. 



Found at Koonmooh, Rotta Roh. 



Aviculo-pecten, sp. (A-pecten Ovatus, Verch.) PL VI. fig. 6a, and 6b. 



A small specimen, quite smooth. Outline elliptical ; convexity 

 trifling ; ears meeting above the beak into a straight line. 



The inside of the valve shows (5) two strong lateral ridges proceeding 

 from the beak, and terminating about two-thirds down the valve in 

 well defined tubercles. The hinge presents two short rounded ridges 

 or teeth proceeding from the beak for about a quarter of an inch, when 

 they also terminate in minute tubercles. 



Avicido-pecten, sp. (A. • pecten Ranus, Verch.,) PL VI. fig. 7 and 7a. 



Outline sub-circular ; shell very flat ; ears irregular. The whole 

 valve is covered with fine radiate striae, and with thin lines of growth. 

 Shell thin. Internal cast not found. It is perhaps the P. Grenisteria 

 (cle Koninck.) 



Avicido-pecten Circidaris, Verch., PL VII. fig. la. and lb. 



Outline of shell sub-circular, rather transverse. Shell moderately 

 convex ; concentric striae faintly seen. Lines of growth irregular and 

 unconspicuous. The cast (b) presents two deep pits which are 

 continued by a groove towards the beak, corresponding on the inside 

 of the shell to two muscular tubercles and ridges. The ridge is 

 much more defined posteriorly than anteriorly. Lines of growth 

 strongly marked on the cast ? No pearl fossae. It may be a variety of 

 P. Elliptic™ (Phill.) ? ? 



Avicido-pecten, sp. PL VII. fig. 2a & 2b. 



Outline pyriform, umbo-marginal diameter the longest. Moderatly 

 gibbose ; beak much incurved and somewhat imbedded in the ears, 

 which meet above it in a straight line. 



The cast only was found. It shows two strongly marked lines of 

 growth well set apart. No pearl-fossae on cast. 



