38 PEOCEEDIXGS OF THE GEOLOGICAL SOCIETY. 



the ventral ; beak incurved, of moderate projection. Proportions 

 variable. About 13 lints in length and breath, by 10 in depth. 



Of this shell two varieties ajDpear to occur at Kato, which may 

 be distinguished by the number and projection of their ribs. 



§ 3. Cretaceous (?) Species. 



A compact light grey limestone near Lacholung La, north side, 

 in the Sum Country in Thibet, contains in abundance two species 

 of Brachiopoda. The exact age of this rock does not appear to have 

 been hitherto satisfactorily determined ; but as these two Brachio- 

 pods have a very Cretaceous aspect, and as Capt. Godwin- Austen 

 informs me that a rock at a place called Kalatys in the Upper Indus, 

 not above fifty miles from where the Jurassic fossils were found, 

 contains Hippurites, it may not perhaps be impossible that the light 

 compact limestone in question may belong to the Cretaceous period. 

 This point, however, cannot well be determined from the examina- 

 tion of the two species of Brachiopoda therein found, as some- 

 what similarly shaped shells do also occur in rocks of the Jurassic 

 period. 



1. Waldheimia Blanfoebi, spec. nov. PL I. fig. 8. 



Shell obscurely pentagonal, straight or slightly indented in front. 

 Yalves gently convex and smooth, no mesial fold in the dorsal 

 valve, but a gentle depression or sinus occurs near the front of the 

 ventral ; beak small, truncated by a foraminal aperture. Length 

 8|, width 8, depth 4 lines. 



2. Rhyis^chonella, sp. PL I. figs. 9 &10. 



Shell transversely oval, wider than long. Yalves equally deep 

 and convex ; when well-shaped there exists in the dorsal valve a wide 

 very shghtly elevated mesial fold, a sinus being present in the opposite 

 one. The surface of each of the valves is ornamented with about 

 twenty-four angular ribs, of which five or eight occupy the fold and 

 sinus. These last are, however, very often shifted more to the one 

 or to the other side, giving the shell an unsymmetrical appearance. 

 Beak angular ; foramen small, contiguous to the umbone. Propor- 

 tions variable. Length 10, width 12, depth 5 lines. 



This irregularity in the position of the fold and sinus may be 

 occasionally noticed in many species of the genus Bliynclionella, but 

 is particularly prevalent in certain Jurassic forms^ such as 11. in- 

 constans, B. sulcata, U. dimidiata, &c. ; indeed so closely do some 

 of the specimens under description approximate in shape to some 

 specimens of Parkinson's M. sidcata, and to another species to which 

 Sowerby had given the name of B. dimidiata, that I would not ven- 

 ture for the present to indentify the Thibet fossil by any definite 

 specific denomination. 



