62 University of Texas Bulletin 



Of these echinoderms the starfishes and brittle stars have so far been 

 found only in the upper formations, Denton and above. The echinoids 

 also seem more abundant and varied in the Upper Washita; Enallaster 

 particularly shows a development of several species in the Weno and 

 Pawpaw formations. Stenonia supernus (Cragin) is known only from 

 the Grayson marl. Among the small echinoids, Regularia, especially 

 Salenidae, predominate. The Salenidae have a wide distribution and 

 their various species seem reliable as horizon markers. 



CRUSTACEA : 



There is a great variety of crabs belonging to many different genera. 

 Of the lobsters a small species of Hoploparia is abundant in the Denton 

 marl. Segments of appendages abound in these four formations; claws 

 are found in the Duck Creek and Pawpaw and rarely in the intervening 

 formations. These Crustacea are for the most part calcareous and ex- 

 cellently preserved. In addition there are known in the Texas Coman- 

 chean, from the Goodland indeterminate limb segments; from the Duck 

 Creek limestone Callianassa sp. claws; from the Fort Worth limestone a 

 lobster related to Homarus (Dr. Shuler) ; and from the Weno, two lob- 

 sters and an indeterminate claw. A crab and a lobster claw have been 

 reported from the Buda. 



TABULATION OF KNOWN CRUSTACEA OF THE WASHITA PYRITE AND 



LIMONITE FAUNAE 



Duck Creek Denton Pawpaw Grayson 



Species marl marl clay marl 

 ASTACURA: 



Cambarus ? . . . 1 



Hoploparia 1 1 



appendages, indet , . . . . . . . 3 



species, indet . . . . 4 



ANOMURA: 

 Callianassa . 1 



BRACHYURA: 



species indet. 



PELECYPODA : 



The Duck Creek limonite fauna is marked by the relative poverty of 

 pelecypods and the relative abundance of gastropods. A small species 

 of Area, abundant in the Pawpaw also occurs in the other formations. 



