DESCRIPTIONS OF T1IE SPECIES. 237 



disappeared, came from the same neighbourhood. The example which we have 



figured is of a dark red colour, and was found in the Carboniferous Linn-tone of 

 Somersetshire. There is therefore a possibility that it may be the Pentremitea 

 ylohosa of Say, who referred to the type as follows 1 ; — "This large and fine species 

 belongs to the Philadelphia Museum. It was brought from England by Mr. Reubens 

 Peale, who understood that it was found in the vicinity of Bath. None of this 

 species, I believe, has yet been found in America." The measurements of Say's 

 specimen are — " Length one inch and one fifth; greatest breadth one inch and three 

 tenths ;" and these are not very different from the corresponding measurements of our 

 type. Shumard 2 says of Say's specimen that it " most likely belongs to Granato- 

 minus or EUeacrinus" both of them forms which are altogether unlike Pentremites 

 proper. Elaacrinus has ten spiracles, just like Acentrotremites, and this is the chief 

 objection to the suggestion that Say's type belongs to our new genus; for he called 

 it Pentremites globosa, and specially mentioned the five summit-openings as charac- 

 teristic of the genus, of which P. globosa was the first species named by him. 

 Locality and Horizon. Somersetshire: Carboniferous Limestone. 



Family GBANATOBLASTID^E, E. & C, 1886. 



Definition. Calyx globular or ovoidal, with flattened or concave base and linear 

 ambulacra. Spiracles five, piercing the deltoids, or ten, grooving their lateral edges. 



Remarks. This family is closely allied to the Schizoblastidae in the general relations 

 of the calyx and of its narrow ambulacra, but differs from all other Blastoids in the 

 summit characters. In the type genus, Granatocrinus, there is but one spiracle in 

 each interradius, which pierces the central end of the deltoid, and leads inwards 

 through its substance into two hydrospire-canals, that diverge rapidly, and open into 

 the proximal ends of the hydrospire-sacs at its sides (PI. VII. figs. 5-9). No other 

 Blastoid presents anything like this relation of the hydrospire-canals to the deltoid 

 plates, with the exception of the recently discovered Ileteroblastus. In this remarkable 

 type the inner face of each deltoid is marked by two grooves, which lodge the 

 proximal ends of the hydrospire-canals, and have minute external openings at the 

 sides of the ambulacra (PI. VI. figs. 3, 4). The deltoids are thus distinctly excavated 

 to form the internal connections of the spiracular openings, though by grooves only, 

 not by canals ; and these grooves open separately, instead of having a common aper- 

 ture as in Granatocrinus. In abnormal examples of the latter type, however, there 

 may be two openings in the deltoid, as shown in PI. VII. fig. 12 ; and if they were a 

 little nearer to the edges of the plate the canals would be reduced to the condition of 

 grooves as in Heterohlastus. The partial division of the spiracles of G. HcCoyi by 



1 Journ. Acad. Nat. Sci. Philad. vol. ir. pt. ii. p. 294. 



2 Tjans. St. Louis Acad. Sci. 18G5, vol. ii. no. 2, p. 385, 



