Clark — New Genera of UnstalJceal Crinoids. 129 



the radial faces. In Thysanometra these are approximately oblong, 

 broader than long, the muscular fossa; large, transversely ronnded-oblong, 

 separated from the interarticular ligament fossa? by horizontal ridges, the 

 exterior ends of which are more or less curved downward. In Coccometra , 

 as described, these are wedge-shaped, elongate, the muscular fossae elon- 

 gate triangular, separated from the interarticular ligament fossae by 

 strongly diagonal and straight ridges. Externally, Coccometra may be 

 distinguished by its longer arm joints, longer pinnule joints, and short 

 distal pinnules which are not so long as the proximal, while in Thysano- 

 metra they are considerably longer. This is the only comatnlid genus in 

 which the coloration appears to have a systematic value. It includes 

 three species, one which was described by Pourtales, another mentioned 

 by Dr. Hubert Lyman Clark, and a third as yet undescribed. They are, 



C. hagenii (Pourtales). 



('. nigrolineata [=Antedon hagenii H. L. Clark (not Comatula 

 hagenii Pourtales ) , 1901 ] . 



Leptometra gen. now 



Genotype. — Alecto phalangium J. Muller, 1841. 



Radial faces wedge-shaped, very long, nearly, or quite, twice as long 

 as broad, the muscular fossa' much elongated, and sub-triangular, separ- 

 ated by a diagonal ridge from the fossae lodging the interarticular liga- 

 ments, and in close opposition interiorly. Centro-dorsal hemispherical, 

 conical, or somewhat columnar, bearing from twenty to thirty cirrus 

 sockets which may, or may not, be regularly arranged, but are always 

 separated more or less from each other. Cirri very long and slender, of 

 more than forty cylindrical joints, slightly more elongate proximally than 

 distally, squarish, or longer than broad; no dorsal spines; usually no 

 opposing spine. Radials more or less hidden; first costal short, 

 second usually pentagonal, rather large, deeply incising the first; the 

 costals are strongly convex dorsally, and may or may not be in lateral 

 apposition and laterally flattened. Ten long and slender arms of 

 obliquely quadrate or triangular joints, as long as or longer than wide. 

 First two pinnules elongate, slender and flagellate, the first six or eight 

 joints short, the remainder elongate ; following pinnules shorter, but the 

 length of the basal joints gradually increases, except the two first, which 

 become somewhat flattened ; ovaries long and fusiform. 



( 'olor. — Green. 



Geographic distribution. — Mediterranean Sea, west of Italy and Tunis; 

 eastern Atlantic, from the Madeira Islands northward along the coasts of 

 Europe, and west coast of the British Isles to the Hebrides.* 



Depth.— 45 to 189 fathoms. 



The great length of the muscular fossa in this genus which are not in- 

 teriorly separated by a notch is sufficient to distinguish it at once. Exter- 

 nally the elongate and slender cirri, which are smooth with very numerous 



* Reported also from Hope, or Seahorse, Island, just southeast of Spitzbergeu ; but 

 Grieg has already called attention to the fact that this is probably a ease ofmisidentifi- 

 eation. 



