282 CATALOGUE OF THE BLASTOIDEA. 



Pentremites Schuhii, Mallada, Bol. Com. Mapa Geol. EspaBa, 1875, tomo ii. p. 79, lam. 12. 



f. 7, 8. 

 Pentremitidea SchuUzii, E. & C, Ann. & Mag. Nat. Hist. 1882, vol. ix. p. 223. 



Sj). Char. Calyx claviform, forming in its upper part a rapidly expanding short 

 cup ; base slender, elongate, and stem-like ; summit greatly expanded and abruptly 

 truncated, the wide and flattened ambulacra giving to it a rosette-like appearance. 

 Basal plates very much lengthened, and divided into two portions by a transverse 

 fold-like constriction ; the upper part of the united basals forms a cup of variable 

 height, whilst the lower end is stem-like. The interbasal sutures sometimes curve 

 considerably towards the bottom, so that the section is equally tripartite. Radial 

 plates short, broad, and almost quadrangular ; bodies but little convex ; sinuses 

 very shallow and short, the proximal ends of the radials being hardly excavated to 

 form them. Visible parts of the deltoid plates exceedingly small, long, and cristi- 

 form. Ambulacra strongly petaloid or even deltoid, short and wide, flattened or a 

 little concave ; lancet-plate elongately petaloid ; side plates fourteen on each side, 

 narrow and oblong ; outer side plates very small, placed at the extremities of the 

 side plates, and nearly on the same level with them. Spiracles pyriform ; anal 

 spiracle rather larger than the others. Hydrospire-tubes five to eight on each side, 

 the two inner ones the longest. Mouth large. Ornament of very fine concentric 

 striae. Column of strong thick joints ; canal very small. 



Remarks. The combination of the broad and flattened summit of this species with 

 its elongated base gives it a very characteristic appearance in side view, especially 

 when the calyx is bent over above the constriction in the basal cup (PI. V. figs. 25, 

 26). The peculiarities of this structure have been already alluded to l , and need not 

 be farther discussed. 



The deltoid plates are normally limited to the summit, where they are so largely 

 covered by the petaloid ambulacra that only their extreme outer ends are visible 

 (PI. V. fig. 23). Sometimes, however, one of them just appears on the side of the 

 calyx (PI. V. fig. 24) ; and it may also happen that the ambulacra do not reach so 

 high on to the oral ridges as usual, thus causing the spiracles to be double instead of 

 single, and exposing the entire length of the deltoid plates (PI. XIII. fig. 20). 



The number of hydrospire-folds appears to be somewhat variable. The section 

 represented in PI. XVIII. fig. 2, shows eight on each side; but only six are visible 

 in PI. V. fig. 24 and PI. XVI. fig. 3, while there are only five in fig. 4 on the latter 

 plate. This, however, represents their terminations in the body of the radial, which 

 only receives but a very small portion of the uppermost fold on each side of the sinus. 



Cryptoschisma Schu/zi is such a well-defined specific type that it cannot be mis- 

 taken for any other Blastoid with which we are acquainted. The name of this species 

 has been spelt in several ways, we ourselves having been in error when referring to 



1 Antea, pp. 15, 16, 20. 



