732 



688 " THETIS " SCIENTIFIC RESULTS. 



6^. Cirri pi'eaent ; elements of division series united by synarthry 



, Comatella. 



a'. The proximal pinnules do not bear terminal combs ; mouth 

 central ; anal tube marginal. 



h^. Pinnules triangular , Ptilometra. 



b''. Pinnules cylindrical. 



c^. Po much enlarged, abruptly larger than P^ or P3, which 



latter resemble P4, stiff and spinelike ; the division 



series are well separated, and their component ossicles 



have broad ventrolateral processes. 



d^. Cirrus segments subequal, all much broader than long, 



the outer with paired dorsal spines Cenometra, 



d"^ . Earlier cirrus segments (except the basal) longer than 

 broad, but becoming shorter distally ; outer cirrus 



segments without dorsal processes Stephanometra. 



c^. Pg not greatly, if at all, larger than P^, which latter is 

 considerably larger than P^^ ; enlarged proximal pinnules 

 flagellate, with very numerous segments ; division series 

 in close lateral apposition, and usually laterally flattened, 

 without ventrolateral processes on the component seg- 

 ments Dichrometra. 



Kkt to the Genera of Australian Crinoids containing Species with 



MORE THAN TEN ARMS WHOSE II Br SKRIES ARE 4 (3 + 4). 



a^. The proximal pinnules bear terminal combs ; mouth more or less 

 excentric, anus more or less central. 

 lA, Combs occur at intervals along the distal pinnules ; proximal 



pinnules slender; mouth nearly central Cotnasier. 



b"^. Combs confined to the proximal pinnules, which are stouter 



than those succeeding ; arms nearly or quite central Comanthus. 



a*. Proximal pinnules without terminal combs ; mouth central, anus 

 marginal. 

 b^. I Br united by pseudosyzygy ; disk completely -plated. ...Zygometra, 

 b"^. I Br united by synarthry ; disk unplated. 



c^. Distal brachials exceedingly short and discoidal ; arm bases 

 rugged and tubercular ; lateral processes on the seg- 

 ments of the proximal pinnules Amphimetra. 



c^. Distal brachials wedge-shaped, not especially short ; arm 



bases smooth ; no lateral processes on the lower pinnules. 



d^. Cirri long and smooth, stout basally and tapering 



evenly to a point Craspedometra. 



d"^. Cirri shorter, not tapei"ing distally, the outer segments 



strongly oarinate or spinous dorsally ..Heteromttra. 



Khy TO THE Australian Species of the Genus Comatella. 



a^. About twenty arms ; cirri small, with 15-20 segments {Queens- 

 land) O. maculata. 



o'. About thirty arms ; cirri well developed; with 20-26 segments 



(Queensland; New South Wales) C. stelligera. 



Key to the Australian Species of the Genus Comatula. 

 al. Twenty arms ; cirri absent. 



6*. All the arms of equal length (iV. and N. W. Australia)... C. rotalaria. 



