North American index fossils, invertebrates . Fig. 1918. Cidaris texana. «, test restored, X K 5 ^ interambulacral plate en-larged ; c, tubercle much enlarged ; d, portion of ambulacral area enlarged. (AfterClark.) 586 NORTH AMERICAN INDEX FOSSILS. 18. C. texana Clark. (Fig. 1918.) Comanchic. Test large. Ambulacral areas with four rows of granules be-tween the pore-bearing zones on the under side, increased to sixat the ambitus and reduced to two at the apex. Pores oval, sepa-rated by transverse ridges which partially envelop the circular, depressed. Washita of Texas. XI. Leio
North American index fossils, invertebrates . Fig. 1918. Cidaris texana. «, test restored, X K 5 ^ interambulacral plate en-larged ; c, tubercle much enlarged ; d, portion of ambulacral area enlarged. (AfterClark.) 586 NORTH AMERICAN INDEX FOSSILS. 18. C. texana Clark. (Fig. 1918.) Comanchic. Test large. Ambulacral areas with four rows of granules be-tween the pore-bearing zones on the under side, increased to sixat the ambitus and reduced to two at the apex. Pores oval, sepa-rated by transverse ridges which partially envelop the circular, depressed. Washita of Texas. XI. Leiocidaris large, swollen. Differs from Cidaris in having the twopores of each pair distant and united by a groove. Tubercles.
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