272 CATALOGUE OF THE BLASTOIDEA. 



the summit, just like those of Codaster, the radio-deltoid sutures descending the sides 

 of the sinuses and meeting the ambulacra (PL XI. figs. 1-3, 5, 6 ; PL XIV. figs. 9, 

 11, 12). These are extremely variable in their character, being sometimes narrow 

 and linear as in P. nohile and P. Verneuili (PL XI. fig. 4 ; PL XIV. fig. 9), and 

 sometimes so broad as to conceal the greater part of the hydrospire-slits as in 

 P. caryophyllatum, P. Archiaci, and P. acutum (PL XIV. figs. 3, 4, 6, 11). The 

 proximal side plates of these three species project considerably beyond the edges of 

 the lancet-plate and so bridge over the lower part of the radial sinus, thus converting 

 it into a canal on either side of the lancet-plate ; and there are minute spiracular 

 openings round the mouth by which these imperfect hydrospire-canals communicate 

 with the exterior, though they can also do so through the uncovered ends of the 

 hydrospire-slits. In P. caryophyllatum and P. Archiaci these are the distal ends 

 (PL XIV. figs. 3, 4, 6), but in P. acutum, so far as we can make out, it is the distal 

 ends of the slits which are covered by the ambulacra (PL XIV. fig. 11). Our best 

 example of this species approaches rather closely to Cryptoschisma, as no slits are 

 visible at all in one interradius, though in other parts of the calyx one may be seen 

 above the ambulacrum. In P. caryophyllatum we often find one entire slit exposed, 

 with the distal ends of four or five others (PL XIV. fig. 3), while in P. Archiaci two 

 slits are completely visible and four others partially so (PL XIV. fig. 6). In the 

 species with narrow ambulacra, however (PL XI. figs. 1-6), the great majority of 

 the slits are altogether uncovered. 



All the species but P. caryophyllatum have a narrow lancet-plate, which is com- 

 pletely concealed by the side plates (PL XI. figs. 3, 4; PL XIV. figs. 5-7, 9, 11); 

 but in this curious type they simply lie against the lancet-plate as in Pentremites 

 and do not cover it at all (PL XIV. figs. 2, 3), so that in this respect it approaches 

 Cryptoschisma more closely than P. acutum does. 



The absence of the deltoids from the exterior of the calyx readily distinguishes 

 Phcenoschisma from Orophocrinus, some forms of which (PL XIV. figs. 14, 17) 

 approach it rather closely in other respects. The anal aperture varies in its 

 character according to the species. For instance, in P. Archiaci the contiguous 

 limbs of adjacent radials forming the anal interradius are shortened and truncated, 

 so as partially to surround the anus (PL XIV. fig. 5). In P. acutum, PhilL, sp., on 

 the other hand, the cristiform aspect of the other interradii is in no way altered in 

 the azygos interradius, and the surface of the anal deltoid is hollowed out for the 

 partial reception of the aperture (PL XIV. fig. 11). 



Species. The following is a list of the species which we refer to Phwnoschisma : — 

 Pentatrematites acuta, G. B. Sowerby. Carboniferous Limestone; Lancashire. 

 Phcenoschisma Archiaci, E. & C. Lower Devonian; Leon and Asturias, Spain. 

 Phamoschisma Benniei, sp. nov. Lower Carboniferous Limestone; Scotland. 



