Prof. J. Miiller on the Structure of the Echinoderms. 249 



unite the pores belonging to an entire series of pores,, which 

 penetrate the entire thickness of the plates^ so that the series of 

 pores appear also upon the inner surface of the plates. Some- 

 thing similar may also be observed in many specimens of Caryo- 

 cystites granatum, inasmuch as the canals of the bands not un- 

 frequently also exhibit clefts here and there between the terminal 

 pores. These clefts may indeed be readily explained by the 

 grinding down of the canals ; the occurrence of the regular rows 

 of pores in the species above mentioned, however, leads us to 

 question whether they always have this origin. 



c. In Echinosphcerites aurantium and aranea eveiy two pores 

 of two plates are not uncommonly connected by one, usually by 

 two canals, which are recognizable upon the outer surface of the 

 plates ; Echinospharites testudinarius, included by Von Buch in 

 the ill-defined genus Caryocystites, is an elongated Echinosphse- 

 rite. Its pore-rhombs agree more closely wdth the previously- 

 named species than with Caryocystites granatum, though the 

 number of the pore-canals between every pair of pores is in some 

 localities still greater. In fact, we not unusually observe not 

 only two, but three, or even four conjoined canals, which open 

 at both ends into a pore, and are so connected. 



d. The genera Echino-encrinus, PseudocriniteSy Apiocystites, 

 Prunocystites, are distinguished by possessing only a few pore- 

 rhombs — fragments of the system — w^hich however are here 

 justly termed pore-rhombs. In Echino-encrinus angulosus and 

 striatus there can be no doubt that the elongated pores of these 

 rhombs are clefts w^hich penetrate the whole thickness of the 

 plates. Forbes remained in doubt with regard to these pores, and 

 was inclined to interpret the 'pectinated rhombs^ as the situation 

 of ciliary organs comparable with the ciliated epaulettes of the 

 larvae of Echini, Seeing the very problematical nature of all 

 pore-rhombs, and of all non-ambulacral pores of the Crinoids, in 

 fact, the supposition that the cilia are connected with the pores 

 and pore-canals is not to be excluded. 



The number of the pore-rhombs in the Echino-encrinites ap- 

 pears to vary, and Echino-ena'inus granatum, Volb., would appear 

 to be only such a variety of the E. angulosus. 



II. Cystideans with double pores upon the calycine plates, 

 which belong not to two different plates, but to the same. The 

 plates are facetted, and each facet possesses two closely approxi- 

 mated pores. Here belongs a small group of Cystideans, which, 

 since it consists of many genera, might be called Diploporitida 

 (Diploporiten) . The genera included in it are : — 



1. Sphceronites pomum. His. Type of a peculiar genus, which 

 may retain the name of Sphceronites, as opposed to the Echino^ 

 sphaerites with pore-rhombs. 



