338 REPORT ON THE STATE CABINET. 



NOTE ON THE GENUS TJINIASTER, Billings. 



The Genus T^niaster is thus described : 



" Generic characters: Body deeply stellate; no disc or marginal plates; rays 

 long, slender, flexible, and covered with small spines; two rows of large 

 ambulacral pores; adambulacral plates elongated and sloping outwards, 

 so that they partly overlap each other: adambulacral ossicles contracted 

 in the middle, dilated at each end." 



Mr. Billings remarks that this genus differs from Protaster (as 

 described bj Mr. Salter in the Annals and Magazine of Natural History, 

 November 1857) in the following particulars : 



" 1. Peotaster has a well developed disc;" 



"2. It has also the pores outside of the ambulacral ossicles [see Mr. Saltee's 



tig. 40 in the article above cited];" 

 " 3. The same figure shows that the oral plates of P. miltoniAve formed of two 



of the ambulacral ossicles, instead of two of the adambulacral plates." 



In reviewing the characters of Protaster and Eugaster, I became satis- 

 fied that there was an intimate relation between these and T^niaster of 

 Billings ; and in order to satisfy myself on this point, I have, since the pre- 

 ceding pages were printed, requested, and liindly received from Sir William 

 E. Logan, permission to examine specimens of Tceniaster spinosus and T. 

 cylindricus (Decade iii, Canadian Organic Remains, Plate x, figs. 3 and 4). 



An examination of the specimen illustrated in fig. 3 (ut. sup.) reveals 

 what I conceive to be a disc not at all unlike the disc of Protaster, but 

 less extended than in the Lower Helderberg species. The structure of 

 the ray is precisely of the same character as the ray of that species 

 which I have named Protaster forbesi, the proportions of plates and rela- 

 tions of parts showing specific differences. 



It is true that the figure of Mr. Salter represents the oral ossicles as 

 proceeding from the ambulacral plates ; a feature which I think can 

 scarcely exist, and the representation is probably due to an oversight, or 

 to a distortion of the specimen. I believe, moreover, that on examina- 

 tion of more perfect material, Mr. Salter will ascertain that the position 

 of the pores is not precisely as represented. 



Mr. Billings remarks, under the description of T. spinosus, that " the 

 ambulacral ossicles appear in some places to alternate with each other, 

 but this is owing to a distortion ; those on one side of the furrow are 

 opposite to those upon the other."* 



* Canadian Organic Remains, Decade iii, p. 81. 



