New Fossils from the Bokkeveld Beds. 401 



present collection ; and it may be mentioned that the shells from 

 Argentina which Thomas ''■'■ regarded as young individuals of Lio- 

 rhynchus bodenbenderi Kayser bear a consideraljle resemblance in 

 general shape and ribbing. In some of our examples a coarsely 

 punctate structure of the shell, as in Retzia, seems to be present. 

 Unfortunately the critical internal features for the determination of 

 the true generic position of these little shells are insufficiently 

 preserved. 



The style of ribbing and the number of ribs (about 20) in the 

 present specimens agree with Schwarz's description and figure, and 

 the shell seems only distinguishable from my Trigeria aff. (jaudryi 

 by having the ribs less numerous, as in the latter they number 

 28-30. 



The true relations and generic determination of the ribbed shells 

 which have been described from the Bokkeveld Beds as Bhyncho- 

 spira ? silveti, Betzia cf. adrieni, Trigeria aff. gcmdryi, Trigeria 

 simplex and Bensselceria sp. /3 must remain unsatisfactory and 

 unsettled so long as the material available is so poor. 



Localities. — Zwartberg Pass, Gamka Poort, Boschlui's Kloof, 

 Gabbosch Lagte, Ladismith, Worcester, ? Hex Eiver Mountains. 



Genus RENSSELiEEIA Hall, 1859. 



RENSSEL^RIA MONTAGUENSIS sp. nov. 



(PL XLVIIL, figs. 5-7.) 



There is a species of Bensselceria from Montagu which is repre- 

 sented by many more or less crushed fragmentary casts of shells, 

 from which the following somewhat incomplete description of what 

 is undoubtedly a new species can be drawn up. 



Shell broadly oval, widest across middle, about 1^ times as long 

 as wide, unequally biconvex. Pedicle-valve more convex than 

 brachial, with strongly elevated prominent beak, arched over and 

 rising a little above hinge-line, with small concave area below 

 extending laterally into narrow cardinal area. Dental plates thin, 

 sHghtly divergent, short. Weak median ridge in beak. Brachial 

 valve less convex than opposite valve, with small inconspicuous 

 beak ; short median septum thickening towards beak, dividing 

 adductor scars which are strongly impressed anteriorly ; stout hinge- 

 plate composed of a pair of rounded cushions fused together, grooved, 

 and perforated medianly by minute pit on anterior face, but not 



* Thomas, oj). cit., t. xiv., tigs. 33, 34 (mm 31, 32). 



