1887.] NATURAL SCIENCES OF PHILADELPHIA. 113 



the latter we find a number of genera, in wliich the arrangement of 

 of the dorsal cup is altogether symmetrical. 



It will not, of course, be inferred from the foregoing remarks that 

 we think Allagecrinus and Haplocriniis belong to the Neocrinoidea, 

 but simply that, if Messrs. Ether idge and ('arpenter's arguments 

 are valid, they necessarily lead to that conclusion. We think, on 

 the contrary, there are the strongest reasons for considering them 

 both to be Palaeocrinoids, and that there is no difficulty in discover- 

 ing entire conformity in their morphological conditions with other 

 Palaeocrinoids. 



Whatever arguments Messrs. Etheridge and Carpenter may here- 

 after offer in favor of their oral theory, it seems to us, they will have 

 to explain ujjon palaeontological grounds how the five large ventral 

 plates of Allagecrinus and Haplocrinus which cover the whole ven- 

 tral surface happen to occupy in all higher or more advanced forms 

 a comparatively small space around the peristome. They will have 

 to point out by what process the jive plates, without coming in con- 

 tact with the anus, were transformed into six pieces or more ; and 

 they will have to furnish better proof as to the existence of a so-called 

 "orocentral," or they will have to modify their generalizations, which 

 are basqd almost exclusively upon this highly hypothetical plate. 



Explanations of Figures, Plate IV. 

 (The following letters are employed throughout the figures). 



o. Oral plate or oral pyramid ; p, proximals ; i, interradials ; 



i a, interaxillaries ; r, radials ; a, anal plate ; x, anus , g, grooves. 

 Fig. 1. Oral pyramid and surrounding plates of Sphaeronites glo- 

 hosus (after Angelin, Icon. Crin. Suec. Tab. XI, Fig. 14.) 



2. Ventral aspect of Cyathocrinas Gilesi. 



3. The same of Stephanocrinus angulatus. 



4. The same of Haplocrinus mespiliformis. 



5. Profile view of the same species. 



6. Ventral aspect of Caryocrinus ornatus (after Hall, Palaeont. 

 N. York, Vol. II, PI. 41a, Fig. le). 



7. The ventral plates of Caryocrinus from near Louisville, 

 Ky. (The course of the subtegminal ambulacral tubes in- 

 dicated upon the surface of the plates). 



8. The sam e oiJuglandocrinus crassus (after von Koenen, Jahrb. 

 Miner. Bd. II, Taf IX, Fig. 3.). 



9. Ventral covering of a new Talarocrinus from Kentucky ; 

 the peristomial area closed by a large central plate with- 

 out the aid of proximals. 



