50 
Transactioi^s Texas Academy of Science. 
Cragin, F. W . 
Trigonia clavigera sp. nov. ; T. concentrica sp. nov. ; T. securiformis sp. 
nov. ; T. taffi sp. nov.; T. vyschetzkii sp. nov. Venus malonesis sp. nov. 
Vola hellula sp. nov.; V. catherina sp. nov.; V. dupUcicosta, Roem. ; V. 
lorightii, Shuin. Yoldia septariana sp. nov. 
Gasteropoda. Anchera modesta sp. nov. Buceinatrix gen. nov. B. 
regina sp. nov. Cerithium hosquensg, iShum. ; G. interlineatum sp. nov. ; 
C. proctori sp. nov.; G. tramitenses sp. nov. Ginulia tarrantensis sp. nov. 
Gylindrites formosus sp. nov. Fusus graysonensis sp. nov. Natica humi- 
lis ap. nov. N. striaticostuta sp. nov. Nerinea hicoriensis sp. nov. N. 
pellucida sp. nov.; N. volana sp. nov.. Neritina apparata ap. nov. Nerit- 
opsis hiangulatus, IShum.; N. tramitensis sp. nov. Pleurotomaria macil- 
enta sp. nov.; P. rohusta ap. nov. Rostellites pupoides sp. nov. Tricho- 
tropis shumardi sp. nov.; Turhinopsis septariana sp. nov.; Turritella 
coalvillensis, 'Mk. ; T. renauxiana, D’Orh.; T. seriatim- granulata, Roem. 
Tylostoma ? mutabilis, Gahb. 
Cephalopoda. Buchiceras incequiplicatus , Shum. ; B. sioallowvi, iShum. 
Grioceras annulatus, iShuni. Hoplites roemeri sp. nov.; H. texanus sp. 
nov. Nautilus texanus, Shum. P achy discus hrazoensis, Shum.; P. corn- 
plexus, H. and M. Placenticeras syrtalis. Mart., var. nov. cumminsi. 
Pulchellia hentonianum sp. nov. Soaphites septem-seriatus sp. nov. 
Schloenhachia leonensis. Con. ; 8. peruviana. Von B. ; 8. pollgari, Mantell. 
8phenodiscus dumbli sp. nov.; 8. emarginatus sp. nov.; 8. lenticularis, 
Owen; 8. roemeri sp. nov. 
Plates. 
8erpula jonahensis sp. nov. based on illustration. Ostrea roanokensis 
sp. nov. based on illustration. 
56. 
The Choctaw and G-rayiSon Terranes of the Arietina. 
Colorado College Studies, 5th Ann. Pub., pp. 40-48. Colorado 
Springs, 1894. 
• “The ^ram’s horn oyster,’ Exyogyra arietina, F. Roemer, is the character- 
istic fossil of a column of sediments, the so-called Exogyra arietina marl, 
that in Hays, Travis and Williamson counties, Texas, consists mostly of 
calcareo-argillaceous, and more or less ferruginous marl, and attains a 
thickness of sixty to eighty feet, occupying the interval between the top of 
the Washita limestone of Shumard and the base of the 'Shoal Creek Lime- 
stone of Hill. ^ * From LAustin to the Red River valley, in Cook 
and Grayson counties, the Arietina becomes, as Tatf has shown, gradually 
reduced in thickness and decidedly more ■ calcareous. For this calca- 
reous northern phase of the Arietina which, in the Red River valley, occu- 
pies the entire interval between the summit of the Pawpaw clays of Hill 
and the base of the Dakota sandstone. Hill has recently proposed the 
name. Main-street Limestone. 
“The Main-street Limestone, however, consists of two members.. Its dual 
character has been independenitly determined in the field by the present 
writer'., (But the members that compose it were first recognized as terranes 
by Taff in his second Report on the Cretaceous Area North of the Colorado 
