BRACHIOPODA. 29 



extends a not very large triangular platform, which is vaulted, and supported 

 by a median partition not extending beyond its anterior margin. This plat- 

 form is enclosed by low, rounded ridges which originate near the pedicle-furrow ; 

 its surface is flattened medially, but concave on the sides. Of muscular im- 

 pressions nothing can be observed.* In the dorsal valve the cardinal margin 

 is but little thickened and slightly curved. In the middle it bears a thickened 

 process, which is directed somewhat upward and inward, extending partly into 

 the apical cavity of the other valve. From beneath this process, a short thick- 

 ened platform takes its origin ; it is not even on the upper surface, but to all 

 appearances spirally rolled ; it is concave in the middle and bears on both sides 

 elevated crests with sloping lateral faces ; its anterior margin is curved inward, 

 and the whole platform seems to be excavated below. From its sides diverge 

 two bifurcating ridges, and a median septum extends nearly to the anterior 

 margin. Near the lateral margins two sharply defined spaces are enclosed by 

 narrow ridges. The interiors of both valves are marked with radiating strige. 

 Shells small ; shell substance very thin. 



Type, Lakhnina linguloides, Waagen, op. cit., p. 764, pi. Ixxxv, figs. 3-6. 



In the present state of our knowledge, this genus must be regarded as the 

 earliest representative of the Trimerelloid brachiopods. Its occurrence is in the 

 so-called " Obolus-beds " of the Salt-Range of India, in association with several 

 other peculiar inarticulate brachiopodous genera, e. g., Neobolus, Discinolepis, 

 ScHizoPHOLts, etc. At the date of the description of these genera (1885), 

 this formation was considered as conformable with the overlying Carboniferous 

 and Permian rocks of the " Productus-limestone " series, and was, therefore, 

 referred to the Carboniferous age. The fauna bears upon its face a primordial 

 expression, and, before the detailed study of the brachiopods, was regarded by 

 Mr. Wynne, Dr. Stoliczka. and Dr. Waagen himself, as of primordial age. 

 But the subsequent determination by Mr. R. D. Oldham, of great unconformity 



* Dr. Waagen does not consider tlie lateral impressions seen on his figure (which, he says, represent 

 these features too sharply) as of muscular origin, but as the deepened spaces outside the crescent. They 

 certainly are similar in position and extent to the terminal scars as developed in some pjiecies of Monomer- 

 ELLA and Tbimerella. 



