DE8CEIPTION8 01 THE 8PBCIE8. 227 



Granatocrinua melonoides, Meek \ Wortheiij Report Geol. Survey Illinois, 1 s r ■' I , vol. v. 



p. 168, t. 9. fig. 1. 

 Schizoblostua melonoides, E. & ('., Ann. .v Mag. Nat. Hist. 1882, vol. ix. p. 246. 



Sp. Char. Calyx subglobose, melon-shaped ; summit convex and much restricted ; 

 peristome concave; base small, contracted, and more or less flattened ; section deca- 

 gonal] periphery nearly equatorial. Basal plates very small, confined to the central 

 flattened portion of the base. Radial plates long, four fifths the length of the calyx ; 

 bodies very small, turned in at the base; limbs long, obliquely truncated al the 

 upper ends, margins sub-parallel. 1 ach limb has a broad sulcus or depression next 

 the edge of the sinus, extending the whole length of the plate, the surface along 

 the interradial suture swelling into a broad, rounded ridge tapering upwards 

 and downwards ; lips prominent, forming supports for the calyx when in position; 

 sinuses narrow, sublinear, and very long, with parallel sides ; interradial sutures in 

 depressions between the lateral ridges of adjacent limbs. Deltoid plates small, 

 unequally rhombic, concave, and constricted at their central ends. Ambulacra sub 

 linear, depressed below the edges of the sinuses at their proximal ends, but raised 

 above them towards their apices; lancet-plates mostly concealed ; side plates fifty or 

 more. Hydrospires unknown. Spiracles (ten) very small, linear or slit-like, quite 

 apical, and formed as in S. Sayi. Column round. Ornament minutely granular, 

 the granules arranged in more or less wavy lines, parallel to the margins of the 

 plates. 



Remarks. The description of this species by Messrs. Meek and Worthen is clear and 

 comprehensive, as all their descriptions are; but their figure fails to show the broad 

 obtuse interradial ridges which are so characteristic of it, and assist in giving to it a 

 roughly decagonal outline in cross section. The interradial sutures are sometimes 

 placed on these ridges; but they are generally depressed between the ridges of con- 

 tiguous radials. In well-preserved specimens the surface is minutely granular, but 

 the linear arrangement of the granules becomes apparent on weathering. 



Messrs. Meek and Worthen have very justly compared this species with S. Sayi and 

 with Cryptoblastus melo. It is at once distinguished from the former and from 

 S. Rofei (PI. VIII. figs. 9, 10) by the different proportions of its radial plates. In 

 Cryptoblastus melo these plates are very long, like those of >S. melonoides, but there is 

 no trace of the vertical rounded ridges which are seen on the plates of the latter 

 species, and give it so very marked an appearance. Again, in C. melo the basal plates 

 are concealed in a central concavity, but in S. melonoidi.s they are quite flat, or per- 

 haps very slightly apparent in a side view ; while there are hydrospire-pores along 

 the edges of the deltoids, which is not the case in Cryptoblastus. 



Locality and Horizon. Burlington, Iowa : Upper Burlington Limestone, Sub- 

 carboniferous. 



2g2 



