yio. 1685. REVISION OF CRINOID FAMILY COM AST ERID/E~C LARK. 495 



Carpenter. These plates appear to represent the side phites of the 

 Pentacrinitid.T, Tropionietrida\ Thahissometridae, Antedonidw, etc., 

 although performing the function of both side and covering plates. 

 The latter are phylogenetically more advanced structures; whereas 

 side plates are phylogenetically the thin produced ventrolateral bor- 

 der of the pinnulars and brachials which has become separated from 

 the parent ossicle by suture, so covering plates are the produced inner 

 distal angles of the side plates which have become secondarily sep- 

 arated oH'. 



KKV TO THE UKNERA OF THE COMA.STEKn).E. 



«'. Six itinnulos followiiii,' the tirst jiair absent; month always central. 



(1) COMATILIA. 



r/^ All plnnnles present: month nsnally more or less eccentric. 



W. IBri and: and first two joints after each axillary nnited by syzygy. 



(2) COMATULA, 



&'. IBri and; and first two joints after the tirst axillary nnited by syuarthry. 

 c\ Cirri present. 



d}. Cirri without dorsal spines (ten arms). 



e\ First two pinnules much stouter than the succeeding; cirri long, 



slender, and numerous (XL) (3) Cominia. 



e^ P^irst two pinnules more slender than the succeeding ; cirri short 



and stout, few in number (to XXVII) (4) Comactinia. 



(Z^ Cirri with dorsal spines or projections (ten or more arms). 



e\ Distal pinnules exceedingly slender with greatly elongated joints- 



which have expanded articulations; ten arms_(5) Leptonemaster. 



e". Distal pinnules comparatively stout, the joints rarely over twice as 



long as broad, the articulations not expanded. 



f. Ten arms; synarthrial tubercles prominent; pinnule joints with 



the distal ventro-lateral angle produced (G) Comissia. 



f. More than ten arms; synarthrial tubercles not developed; no pro- 

 duction of the distal ventro-lateral angles of the pinnule joints. 

 g^. First brachial bearing a pinnule on arms arising from a IIBr 

 or subsequent axillary ; a syzygy between the second and 

 third brachials. 

 h}. Brachials in distal half of arm exceedingly short, almost dis- 



coidal ; ambulacra naked (7) Capillaster. 



h^. Brachials in distal half of arm triangular or very obliquely 

 wedge-shaped, nearly or quite as long as broad; pinnule 



ambulacra with large side plates (8) Nemaster. 



g^. First brachial never bearing a pinnule. 



/i\ All division series 2; a syzygy between the first two brach- 

 ials (9) Comatella. 



hj^. Several or all of the division series 4 (3-1-4). 



/\ Proximal iiinnules more slender than the succeeding; combs 



occur at intervals on the distal pinnules (10) Comaster. 



f. Proximal pinnules stouter than the succeeding; no combs 



on the distal pinnules (11) Comanthus. 



c^ Cirri absent ; centro-dorsal a thin pentagonal or stellate plate. 



d\ First brachial bearing a pinnule; first syzygy between the first two 

 brachials (7) Capillaster. 



