TRANSACTIONS OF SECTION D. 921 



Series Troostoblastida. — Fam. Troos^ocnWtf^ (Eth. and Carp.). Elongate 

 forms with linear ambulacra descending sharply outwards from the much restricted 

 peristome. Hydrospire-folds only slightly concentrated, but communicate with 

 exterior through pores, and through spiracles bounded by A and lancet-plates. 

 ( Troostocrmus, Metablastus, Tricwlocrinies.) Eleutherocrinida. Elongate, stem- 

 less, asymmetrical, with four narrow ambulacra, accompanied by unconcentrated 

 hydrospires. Fifth ambulacrum shortened and widened. A minute. {Eleuthero- 

 cmius). 



Series Granatoblastida. — Fam. Nucleocrinidie. Interambulacra show 

 traces of a primitive three plates. Ambulacra linear, and stretching far down the 

 theca, which is ovoid. Hydrospire-folds few and pendent. Spiracles double. 

 Mouth roofed by large plates firmly united into a tegmen. {Nucleocrinus, Schizo- 

 blastus.) Equals Nucleoblastidse (E. and C) minus Cryptoblastus and Acentro- 

 tremites. Orbit remitidce. Theca globular with concave or flattened base. 

 Ambulacra linear, stretching down Xq concavity of base. Hydrospire-folds few 

 and pendent; a hydrospire plate always present (unknown in Heteroblastus). 

 Ilydrospire-folds rarely penetrate A, but long canals pass onward, through, beside, 

 or under them, except in Acentrotremites. ( Orbitremites, Cryptoblastus, Hetero- 

 blastus, Mesoblastus, Acentrotremites). Corresponds to Granatoblastidae (E. andC.) 

 plus Cryptoblastiis, Mesoblastus, and Acentrotremites. Pentephyllid<E. Theca 

 subpentagoual, stemless ; RR asymmetrical. Ambulacra linear, stretching down 

 to base. One shorter than the rest. {Petit fphyllum.) Zygocrinidce. Theca 

 depressed, stemless, asymmetrical, quadrilobate. Four ambulacra between the 

 lobes, accompanied by a single hydrospire on either side. Fifth ambulacrum 

 shortened and widened. A large. (Zygocrinus.) 



Class III. CRINOIDEA. — Epithecal extensions of the food-grooves, ambula- 

 crals, superficial oral nervous system, blood-vascular and water-vascular systems, 

 ccelom, and genital system are continued exothecally upon jointed outgrowths of 

 the abactinal thecal plates (brachia), carrying with them extensions of ihe 

 abactinal nerve system. Brachia, primitively and normally five, always rise from 

 an equal number of thecal plates, * radials ' (RR). Below "these is always a circlet, 

 or traces of a circlet, of iuterradial plates, called ' basals ' (BB). A circlet of 

 radially situate ' infrabasals ' (IBB) may also be present. 



Sub-Class A. Monocyclica. — Base consists of BB only ; aboral prolongations 

 of chambered organ iuterradial ; new columnals introduced at extreme proximal 

 end of stem. 



Order 1. Inadtjnata. — Dorsal cup is confined to the patina and occasional 

 intercalated anals ; such Amb or iAmb as enter the tegmen remain supra-tegmiiial, 

 and not rigidly united. 



Fiiram.IIybocrimd(s(iuc\.Ilybocystis,'WetheThj),St^hanocrinid<e,JIeterocrinida! 

 (inch Herpetocr.), Calceocrinida, Pisocrinidce, Catillocrinidce, Zopkocrinidce, Haplo- 

 crinid(s, Allagecrinida, Symbathocrinidce (incl. Phitnocr., Stortingocr,), Belemno- 

 crinidce (incl. Missouricr.), Plicatocrinidcs, Hyocrinidce, Saccocomidce. 



Order 2. Adtjuata. — Dorsal cup primitively confined to the patina and an 

 occasional single anal ; tegmen solid ; portions of the proximal Br and their Amb 

 send to be rigidly incorporated in the theca. Arms fork once to thrice, and bear 

 pinnules on each or on every other Br. BB fused to three, two, or one. {Eucladocr. 

 and Acrocrinidse ofi'er peculiar exceptions to this diagnosis). 



Group A. Fam. PlatycrinidcB : Sub-famm. Coccocrinince (incl. Hapalocr., 

 Cordylocr.), Cypellocrina; {Cypellocr. = Marsupiocr. PhiW. non Jil&inv.), Plafy - 

 crinince. 



Group B. Fam. Hexae^-inidcp, Acrocrinidce. 



Order 3. Cameeata. — IBr, two in each ray (exc. Stereocr., Hadrocr., Allojnos- 

 allocr.), and often succeeding orders of Br are incoi-porated by iBr in the dorsal 

 cup, while the corresponding Amb are either incorporated in, or pressed below, the 

 tegmen by iAmb ; all thecal plates united by suture, somewhat loose in the 

 earliest forms, but speedily becoming close, and producing a rigid theca; mouth 

 and tegminal food-grooves closed ; arm? pinnulate. 



Sub-Order Melocrinoideci. — RR in contact all round; IBr, quadrangular. 



