(iti 



S. L«;VEN, l)N I'orRTALESIA, A GKNl'S OF ECHINOIDKA. 



ing anteriorly a part of the costal irreuularly fractured, while expanding it posteri- 

 orly beyond the other costaLs '). During tiu- next periods the periproct, ahvays placed 

 on the antero-posterior axis and regularl) transverse, in Peltastes, wiiich appears in the 





Peltastes Stude 

 Coi r. C'l-etai-. 



I'seudusnlcuia :is|)era 

 Et. Oolite. 



(ioniuphorus lunulatu 

 Ag. Cretae. 



Salenia scutigura 

 Ga. Ci-etac. 



Afrosaleiiiii spiu 

 Ah. Ool. 





Aerosaleuia augula- 

 ris CoTTA Oolite. 



.\cr09alenia patella 

 Dks. Cretac. 



Peltastes Valleti 

 Des. Oolite. 



Middle Oolite, affects slightly and equally the costals 1, 4, 5, and the central disk, 

 while in Pseudosalenia, of the same time, it erodes it deeply, permitting the costal 5 

 to resume nearly its normal shape. In (joniophorus, of the Middle Cretaceous time, it 

 expands so as To take in great parts of the surroundings. In Salenia proper, which may 

 l)e followed fi'om early Cretaceous time ii]) to the present period, and in Heterosalenia 

 of the later Cretaceous, the periproct is for the greater part cut <>ut from the costals 

 1 and 5, and thus, while slightly entering upon the central disk, is drawn over to the 

 right, on the axis 1 — i], thus conforming to the rule now prevalent in the majority of 

 the EchinidiD and, partly at least, among the Asteriadea, of having the excretory open- 

 ing [ilaced excentricali\", to tlie right of tlie ant('rt)-])Osterior axis. In view af these 

 marks of a gradual advance, in the Saleniada-, during their geological development, of the 

 periproct, from the hindmost limits of the c<ilycinal system to near its centre, there is 

 some reason for inferring the probable existence, at a remote period, of Exocyclic Sa- 

 lenian forms combining a calycinal system of a nearly intact Crinoidean character with 

 a periproct placed in the iiitcrradiuni of tlie bivium, perhaps even towards its venti'al 

 surface') 



Be this as it ma\', in all the kiio^w n Echiniihe, the Saleniadte not excepted, in the 

 earliest forms as in those of the present era, the periproct is endocyclic. In one of 

 the oldest groups, the Cidaridte, the Crinoidean character of the calyx is still strongly 



") Compare .Vcrosalenia luiranda Gauthiek, Eoliiii. loss, de I'Algei-ie, II, p. SG, pi. XX, tij;-. 109, 110. 

 -) Tliu littli; known Upper Sihiriiiu (.'ystocidaris Zitt. (Echinooystites Wvv. Th.) is <lescril>f(l as having the 

 periproi't inlcrradial. 



