the Morphology and Classification of the Saleniidge. 133 



examined morpliologicallj by those authors, as well as by 

 L. Doderlein * and one of us f. A resume of the different 

 opinions regarding structure and classification is to be found 

 in the Report on the ' Challenger ' P^chini, A. Agassiz, 1881, 

 p. 50 et seq., and its perusal leads at once to the belief in the 

 necessity for an amended diagnosis of the genus. 



A. Agassiz has placed the various matters under dispute so 

 plainly and fairly, that an amended diagnosis should come 

 from him ; moreover, the knowledge now possessed of the 

 recent forms is mainly due to him. The recent species of 

 Salenia form a little group in which, with one exception 

 {S. Pattersom, A. Agassiz), there are fewer ambulacral plates 

 than in the Cretaceous forms, and even fewer than in the 

 Tertiary species. The radial plate no. I. is often in contact 

 with the periproct in the recent forms, although there is some 

 variability of this position in the same species. This entry 

 has been noticed in Mesozoic species also, but it is not of any 

 classificatory importance. The abruptness of the transition 

 from the typical form of Salenia to the recent forms is dimi- 

 nished by the presence of Salenia Blanfordi^ Dune, and Sladen 

 (Pal. Ind. ser. xiv. Foss. Ech. of Sind, 1881, p. 29, pi. vi. 

 fig. 4 (Eocene) ), in which the recent characters are distinctly 

 observed, although the ambulacral plates are more numerous 

 than in the recent Salenia hastigerina^ A. Agass., and S. 'pro- 

 fundi^ Dune, for instance. Salenia tertiariay Tate, is from 

 the Miocene of Australia and belongs to the modern type. 

 Lately, and mainly owing to the kindness of A. Agassiz in 

 providing one of us with a specimen of the recent Saleyiia 

 Pattersoni^ A. i^g., some important additions have been made 

 to the morphology of the genus ; moreover, the examination 

 of a very well-preserved specimen of Salenia petalifera from 

 the Upper Greensand has presented some interesting struc- 

 tures to view for the first time. The new facts regarding the 

 structures of these species necessitate some alteration in the 

 generic diagnosis. The perignathic girdle of the modern 

 form is the same as that of the ancient species, and whilst 

 both resemble those of Acrosalenia and Peltastes they are very 

 different from the structure seen in the Cidaridte. In both of 

 the above-named species there is distinct doubling of the pairs 

 of pores, each pair in a peripodium, close to the peristome, and 

 it is evident that demi-plates occur there. This appearance is 

 most marked in S. Pattersoni and in no other recent form, but 



• Doderlein, Arcliiv fiir Naturgesch. Jabrg. 51 (1885), Bd. i. pp. 73- 

 112. 



t P. Martm Duncan, Ann. k Mag. Nat. Hist. ser. 4, vol, xx. pi. ii. 

 p. 70, pi. vii. p. 245. 



