CLARK] NEW GENERA OF RECENT FREE CRINOIDS 359 



to combine the two, at least for the present. The known species of 

 Ptilometra are : 



Ptilometra anthus (A. H. Clark) Ptilometra macronema (J. Miiller) 



longicirra (P. H. Carpen- macropoda (A. H. Clark) 



ter) 



14. THALASSOMETRA, gen. nov. 



Centro-dorsal more or less conical or columnar, the cirri in 10 or 

 15 vertical rows (rarely without definite arrangement), often in 

 pairs or groups of three, separated from each other by ridges; cirri 

 long and slender, with 25 to 90 segments, the lower longer than 

 wide, the distal short and bearing strong dorsal spines ; disk always 

 well plated, ambulacra well plated ; costals united by bifascial articu- 

 lation, deep, strongly "wall-sided ;" ten to thirty arms, long, more or 

 less (often much) compressed and carinate, at least distally, the 

 terminal segments not incurved; distichal and palmar series usually 

 2, rarely 4 (3 -)- 4) ; first syzygy usually between the third and 

 fourth brachials (except when the arm springs from an axillary 

 united to the preceding segment by syzygy, in which case it is be- 

 tween the first and second) ; other syzygies distributed more or less 

 irregularly; first pinnule the largest, long and stout, often greatly 

 enlarged, composed of rather short, but not numerous, segments ; 

 other pinnules of moderate length, or rather short, stiff, rather stout, 

 prismatic, the segments moderately elongate, the first two more or 

 less laterally expanded and trapezoidal; terminal pinnules small, 

 becoming gradually very short at the tip of the arm, beyond which 

 they do not extend ; the genital pinnules are rarely ( ? never) spe- 

 cially differentiated. 



Color in life bright yellow or yellow and white, sometimes the 

 calyx, rarely the whole animal, dull greenish or brownish. 



Type of the genus.— Antedon villosa A. H. Clark, 1907. 



This genus includes the larger part of Dr. Carpenter's "Basicurva 

 group," together with part of the "Spinifera group," and one species 

 placed by him in the "Granulifera group" (in addition to being in 

 the "Basicurva group"). Several additional species have been 

 described since the Challenger report was written, and I have also 

 examined a few others as yet undescribed. Tlialassometra has a 

 very wide distribution, occurring pretty generally throughout the 

 tropics, and north to Bering Sea and the coast of Portugal, south to 

 Australia and South Africa. The following described species belong 

 to this genus : 



