LOWER PALEOZOIC GASTEROPODA — ETHERIDGE. 75 



Genus Trochonema, Salter, 1859. 



(Canadian Organic Remains, 1859, Dec. 1, p. 24). 



Trochonema etheridgei, Johnston. 



PI. xvi., Figs. 5 and 6. 



Trochonema etheridgei, Johnston, Geol. Tas., 1888, t. 5, f. 13 

 and 14. 



Sp. char. — Shell tux-binate, of five or six acutely keeled and 

 angular whorls, the principal keel occupying the periphery of 

 each whorl ; on the anti-penultimate whorl there are three keels, 

 the first small aixd thread-like bordering the upper suture, the 

 surface thence to the second keel being tabulate or flat, from the 

 latter to the principal keel slightly oblique and concave, and 

 thence to the lower suture the surface is straight-walled ; the pen- 

 ultimate whorl possesses four keels besides the peripheral, the 

 three upper arranged as in the anti-penultimate, whilst between 

 the third and fourth the surface is again straight-walled ; the 

 body whorl (somewhat hidden in matrix) probably possessed four 

 also, the peripheral keel being strong and prominent. Sutures 

 excavated. Mouth almost rhomboidal ; outer lip strongly angled 

 at the peripheral keel, rounded below ; inner lip possibly straight. 

 Umbilicus distinct. Sculpture consisting of oblique sub-imbricat- 

 ing growth lamellfe, faintly varicose along the peripheral keel, and 

 becoming much stronger and rugose towards the mouth on the 

 body whorl. 



Ohs. — This well marked shell was figured but not described by 

 Mr. Johnston. In his plate explanation the author remarks that 

 T. etheridgei is allied to T. tricarinata, Meek,* of the Corniferous 

 Group of North America. T. tricarinata, Meek, should be known 

 as T. meekiamim. Miller. f The present shell is readily dis- 

 tinguished from T. montgomerii, mihi, by its much more turbinate 

 form, and difterent arrangement of the spiral keels and sculpture. 



Log. and Horizon. — Gordon River, West Tasmania. Gordon 

 River Limestone, Lower Silurian. 



Trochonema montgomerii, Eth.,fiL 



Eunema montgomerii, Eth., fil., Ann. Rep. Secy, for Mines Tas. 

 for 1895-6 (1896), p. xlvii., pi. f. 21 and 22. 



Ohs. — Since the publication of this species, further examples 

 have been received from the Tasmanian Museum, one with an 

 umbilicus exposed. This will necessitate its removal from Eii,nema 

 to Trochonema. The following additional features may be noted : 



* Ohio Geol. Report, Pal. I., 1873, p. 218, t. 19, f. 5 a and h. 

 t N. American Geol. and Pal., 1889, p. 428. 



