228 Messrs. K. Etheridge, Jun., and P. H. Carpenter on 



Pentremites^ except as regards the oral plates, which resemble 

 those of the former genus. 



Spiracles, in the true sense of the word, do not exist in 

 Phcenoscliisma. At the same time there are visible in Ph. 

 acuturn^ Pliill. s})., some small openings at the central ends of 

 the ambulacra, which may serve as such, and coexist with the 

 exposed hydrospire-slits. They are imperceptible in Ph. 

 Archiaci, nobis, but are present to some extent in Ph. 

 can/ophi/Uatuni, de Kon. sp. 



The species vary considerably in the amount of ex])osure 

 of the hydrospiral slits. In Ph. acution one slit is usually 

 visible for the greater part of its length, though it may some- 

 times be entirely concealed upon one side of an ambulacrum. 

 Ph. caryophyllatum shows one uncovered slit and the distal 

 ends of four or five others, Avhile in Ph. Archiaci two slits 

 are completely visible and four others partially so. 



Finally, the exposure is carried to the greatest extent in 

 Ph. Verneinlt, nobis, which has the majority of its slits 

 uncovered. 



So far as the genus is at present known to us, the form, 

 with one exception, is elongately pyriform. The abnormal 

 species is Ph. caryopJiyllatum^ whicli is a shorter, rounder, 

 and more depressed species than any of the others. Similarly 

 the ambulacra are narrow in all but this species, where they 

 become to a certain extent petaloid. Again, the side plates, 

 except in the same species, lie actually on the lancet-plate, 

 and not against it as in Pentremites. This is a feature which 

 is very characteristic of the genus Granatocrinus, and is again 

 seen in Pentreimtidea. 



The retention of the small and incunspicuous orals at the 

 summit of the calyx, so that they are invisible in a side view, 

 is a very marked feature in Phamoschisma, and a constant 

 character tlu-oughout the genus. They are of larger size in 

 the aberrant Ph. caryoj^hyUatum than in any of the other 

 species. We have succeeded in exposing the watervascular 

 ring of this genus, and tind that it is of essentially the same 

 character as that of Pentremites^ Orojjhocrinus, and Granato- 

 crinus. It is perhaps a little smaller, and the canals leading 

 from the apertures in the lancet-plate rather longer. 



The anal aperture varies in its character according to the 

 species. For instance, in Ph. Archiaci the contiguous limbs 

 of adjacent radials forming the anal interradius are shortened 

 and truncated, so as partially to surround the anus. In Ph. 

 acuturn^ Phill. sp., on the other hand, the cristiform aspect of 

 the other interradii is in no way altered in the anal inter- 

 radius, and the surface of the oro-anal plate is hollowed out 

 for the partial reception of the aperture. 



