354 SMITHSONIAN MISCELLANEOUS COLLECTIONS [VOL. 50 



8. ZENOMETRA, gen. nov. 



Centro-dorsal long, conical or columnar, divided by five inter- 

 radial ridges, often very high, each radial area containing two verti- 

 cal rows of cirrus sockets ; cirri long, with about 50 segments, the 

 basal half of which are greatly elongated, the distal very short, bear- 

 ing prominent dorsal spines ; disk and ambulacra naked ; ten arms ; 

 costals and lower brachials in close apposition and strongly "wall- 

 sided," more or less covered with small spines ; pinnules all much 

 elongated, the first joint, as well as the others, greatly elongated. 



Color in life not recorded; in spirits, pinkish. 



Type of the genus. — Antedon columnaris P. H. Carpenter, 1881. 



Zenometra is most closely related to the Pacific Psathyrometra, 

 which it represents in the Caribbean Sea. One species only has been 

 described, but I have examined specimens of one or two others from 

 the West Indies. The only described species of the genus is : 



Zenometra columnaris (P. H. Carpenter) 

 9. PONTIOMETRA, gen. nov. 



Centro-dorsal discoidal, bearing about 40 cirri in two or three 

 marginal rows ; cirri long, with 50 to 70 very uniform short seg- 

 ments, the distal half of which bear dorsal spines ; disk and ambu- 

 lacra unplated ; radials much wider than the costals, which are 

 rounded and widely separated, not united syzygially; fifty to nearly 

 one hundred arms, all the divisions of two articulated segments ; 

 lower brachials discoidal, soon becoming quadrate (wider than long) ; 

 usually a syzygy between the third and fourth brachial, and others 

 distally at intervals of 6 to 14 bifascial articulations ; first brachial 

 pinnule greatly elongated, slender, tapering, and flagellate, with 

 about 40 somewhat elongated segments ; following pinnules ex- 

 tremely short, with only 6 to 8 segments, increasing slowly in length 

 distally, but never becoming very long. 



Color deep purple or nearly black. 



Type of the genus. — Antedon andersoni P. H. Carpenter, 1889. 



Pontiometra is most closely related to Hiineroinetra, but presents 

 several characteristic features of considerable interest ; the exces- 

 sively elongated first pinnule, contrasting sharply with those follow- 

 ing, the comparative slenderness and consequent wide separation of 

 the costals, the greatly elongated cirri, with very numerous segments, 

 and the comparatively great length of the brachials, the lower of 

 which, together with the palmars, distichals, and costals, entirely lack 

 the peculiar swollen appearance of those of Himerometra, seem to 



