174 
Family Colobometridæ. 
The genera Oligometra, Cyllometra, Colobometra, and Ceno- 
metra differ strikingly from the other genera with which I pre- 
viously associated them in the family Himerometridae; yet they 
exhibit a remarkable homogeneity among themselves which suggests 
that their segregation into a separate family would bring out more 
graphically their systematic relationships. They all agree in having 
short cirri composed of short subequal joints which bear upon their 
dorsal side a transverse serrate ridge, which later passes into paired 
spines or tubercles, and terminally into single spines or tubercles; 
the second pinnule is always enlarged, and either the first or third 
or both may be similar to it; the ends of the component joints of 
the lower pinnules are always more or less prominent, and are 
fringed with spines or expanded into lateral processes; one or more 
of the proximal pinnules is stiffened and more or less spine-like, 
while the middle pinnules usually and the distal sometimes are 
also more or less stiffened; the first inner pinnule is usually absent 
in two out of the four genera. Oligometra and Colobometra are 
exclusively ten-armed, while the species of Cyl/ometra are some of 
them ten-armed, while the others are both ten-armed and multi- 
brachiate. 
Genus Colobometra A. H. Clark. 
Colobometra 1909. A.H.Clark, Proc. Biol. Soc. Washington, Vol. 22, p. 5. 
Colobometra vepretum sp. nov. 
Antedon perspinosa 1891. Hartlaub, Nova Acta Acad. German., Vol. 58, 
No. 1, p. 85, pl. V, fig. 54. 
Centro-dorsal discoidal, rather thin, the bare polar area 3 mm. 
in diameter, concave; cirrus sockets arranged in a single crowded, 
more or less irregular, marginal row, or in two closely crowded 
alternating rows. 
Cirri XX— XXIV, 44—52, comparatively short and stout, 
tapering rather rapidly in the proximal half, slender distally, none 
of the component joints being so long as broad; first joint twice 
