Victorian Fot^slis, Part XII. 313 



in these respects. Another species of the same sub-generic type 

 is 0. {Plectorthia) Ilnarssoni, Kayser,' from the Cambrian of 

 Scandinavia and China. This form, although allied to ours, is 

 not so strongly convex, and differs in the appearance and ar- 

 rangement of the costae. 



The present species differs from the Upper Cambrian orthids 

 of Tasmania indentitied by R. Etheridge, junr. as Orthi>i lenti- 

 cuhiris, Wahlenberg sp.,'- in having a biconvex shell. The latter 

 species appears to belong to the genus OrtJiix sensu stricto, and 

 the brachial valve in that form is nearly flat. Etheridge in his 

 description especially mentions that the Tasmanian specimens 

 are not allied to 0. hickfii, whereas ours clearly show an affinity 

 with that species. 



Class Gasteropoda. 

 Genus SreneUa, Billings, 1S72. 



Scenella tenuistpiata, sp. nov. (PI. LTX., Figs. 18^?, b). 



Description. — Shell small, subconical ; aperture ovate ; apex 

 eccentric, obtuse, slightly incurved towards the longer extremity. 

 In side view boldly convex from apex to margin on shorter 

 side : on longer side concave under the apex, then becoming 

 convex and meeting apertural margin almost vertically. Surface 

 relieved with a few delicate subradial striae inclined towards the 

 longer side, otherwise smooth. 



Dimeihsioitx. — Length, 2.75 mm.; width, 2.4 mm.; height, 

 1.6 mm. 



Affinities. — Practically all the described species of the above 

 genus are from the Middle Camibrian ; but there is an unde- 

 scribed species from the Upper Cambrian (Potsdam Sandstone) 

 of Wisconsin mentioned by C. D. Walcott? which may be at 

 least allied with, our form, as that author compares it with 



1 Orthix MskHii (SaXter), iJav. aff. Lii)arssoii, lS7iJ, Brach. of tlic Paradoxides-hsAH of 

 Sweden,— Bihang: till Svenska Vet. Akad. Handl, lid. iii., No. 12, pi. iii., fi>,'s. 22, 23. 

 0. liiiarssimi, Kayser, 1883, in Richthofeii's "China," vol. iv., p. 34, pi. iii., fij^;. 1. 



2 Rec. Aust. Mus., vol. v., No. 2, 1!»04, ]>. 101, pi. x., fi<rs. bM. 



3 Bull. I'.S. Geol. Surv., No. 30, p. 127. 



