STRUCTURE OF THE CYSTIDEJE. 45 



In fact, we not unusual'y 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, Pseudocrinites, Apiocystites, Pruno- 

 cijstit s, are distinguished by possessing only a few pore-rhombs — 

 fragments of the system — which however are here justly termed 

 pore-rhombs. In Echino-c7icrinus angulosits and E. striatus there can 

 be no doubt that the elongated pores of these rhombs are clefts 

 which 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-cncrinites appears 

 to vary, and Echino-encrinus 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 approximated 

 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 Sphceronit.es, as opposed to the Echinosphcerites 

 with pore-rhombs. 



" 2. Protocrinites (P. ovi/ormis, Eichw.). 



" 3. SphcBronites Leuchtenhergii, Volb., type of a peculiar genus, 

 which may be termed Ghjpfosphcerites. That the Russian Sphceronites 

 pomum, Leuchtenb., or S. Leuchtenbergii, Volb., is not the Swedish 

 S. pomum, Volborth thought probable from Gyllenhal's account. 

 The specimens of the Swedish form in the Mineralogical Museum 

 of this place put this beyond doubt. There are no calycine grooves 

 on the true Sphceronites pomum, His. ; on the other hand, the five 

 outermost calycine plates are elevated into a triangular pyramid, 

 truncated at the mouth, as in Echinosphcerites aurantium ; the edges 

 of the pyramid are broken off in all the specimens, and leave a doubt 

 %% to the form of the arms which were probably present. The base 

 of the calyx is transversely truncated, and very broad in relation to 

 the diameter of the calyx ; it consists of six to seven pieces. 



