Dr. J. W. Gregory — On Pakeozoic Starfishes. 351 



3. SCHUCHEETIA, noY. gen. 

 Diagnosis. 

 Palaeasterinidfe with tessellate exoskeleton ; the rays are short 

 and the general shape is pentagonal. 22 : r as 2:1. Inter- 

 radial plates numerous, polygonal. Adambulacral plates large 

 and hexagonal. Ambulaoral furrow tapering uniformly toward 

 the distal end. 

 Type Species. — Palcsaslerina steUnta, Billings, 1858. Dec. Geol. 

 Surv. Canada, No. iii, p. 76, pi. ix, fig. 1. Trenton Limestone : 

 Ottawa. 

 Aefinities. 



Allied to Palmasterina by the general form of the body and the 

 absence of the marginal plates. Billings clearly doubted whether 

 the fossil could be left in Palceasterina, and he noticed the absence of 

 the spines so conspicuous in the typical species of that genus. The 

 general appearance of the species resembles Lindstromaster, from 

 which it differs by the smallness of the marginal plates. 



Family 3. ASPIDOSOMATIDvE. 

 Diagnosis. 

 Phanerozonia with alternate ambulacral ossicles, large marginal 

 ossicles, and extensive depressed interradial areas. Kays 

 massive, petaloid, subpetaloid, or tapering. 



1. ASPIDOSOMA, Goldfuss, 1848. 



" Ein Seestern aus der Grauwacke": Verb, naturh. Ver. preuss. Rheiul., vol. v, 



pp. 145-6, pi. V. 



Type Species. — Aspidosoma Arnoldi, Goldfuss, 1848. Op. cit. 

 Lower Devonian : Germany. 



2. PAL^OSTELLA, Stlirtz, 1890. 



"Neu. Beitr. palaeoz. Seest." : Paliiaoiitogr., vol. xxxvi, p. 230. 



Type Species. — Palceostella solida, Stiirtz, 1890. Op. cit., 

 p. 230, pi. xxxi, figs. 42, 43. " Ueber verst. und leb. Seest." : 

 Verb, naturh. Ver. preuss. Eheinl., ser. 5, vol. x, p. 42, pi. i, 

 figs. 6-8. Lower Devonian : Germany. 



3. TRICHASTEROPSIS, Eck, 1879. 

 " Bemerk. zii Pohlig iib. Aspidura" : Zeit. deut. geol. Ges., vol. xxxi, pp. 45, 265. 



Type Species. — Asterias cilicia, Quenstedt, 1852. Handb. Petref , 

 p. 596, pi. li, figs. 23, 24. TricJiasteropsis cilicia, Eck, 1879. 

 Op. cit., pp. 43, 265, pi. iv, fig. 3. Muschelkalk : Crailsheim. 



Family 4. T^NIASTEPJDiE. 

 Diagnosis. 



Phanerozonia with alternate ambulacral ossicles. There is neither 

 disc nor interbrachial area. Large marginal plates, of which 

 the inframarginals act as the adambulacral ossicles. Eays 

 long ; petaloid or tapering gradually. 



1. T^NIASTER, Billings, 1858. 

 Dec. Geol. Surv. Canada, No. iii, p. 80. 

 Type Species. — Tceniaster spinosus, Billings, 1858. Op. cit., 

 p. 81, pi. X, fig. 3. OrJovician : Canada. Not Tceniaster cylindnis, 



