12 Clark — A Revision of Thalassometridse a'od Himerometridse . 



present, are inwardly 2, ontwardlj- 4 (3 + 4), whereas in Heteromefra they 

 are always 2. Amphimefra has the same excessively short discoidal bra- 

 chials as Himerometra, whereby it is very easily differentiated from Hete- 

 rometra, though the iii Br series are 2, and Pn is smaller than P, as in the 

 latter. 



n. Dichrometra gen. nov. 

 Genotype. — Alecto flagellata J . Miiller, 1841. 



Centre-dorsal moderate or small, low-hemispherical or discoidal, the 

 bare polar area small, slightly convex, flat, or slightly concave, the sides 

 sloping; cirrus sockets arranged in two or three crowded, alternating, 

 marginal rows. 



Cirri xx-xl, 17-52 (usually 20-30), rather slender and weak, from one- 

 sixth to about two-fifths the length of the arms, the distal joints always 

 somewliat shorter than the proximal (except the basal), though never very 

 short, sharply carinate, or furnished with more or less prominent spines, 

 which, however, are never so long as the opposing spine. 



Radials usually concealed, sometimes slightly visible; di^^sion series 

 always 2, the component joints without lateral processes, though some- 

 times rather sharply carinate ventro-laterally, never very widely separated, 

 usually more or less in apposition and laterally flattened. 



Arms 25 to 43, supernumerary axillaries being always developed exte- 

 riorly in regard to the i Br axillary ; first two brachials wedge-shaped, 

 the longer side out; following five or six oblong, aljout twice as broad as 

 long, then becoming triangular or very obliquely wedge-shaped, about 

 twice as broad as long, then becoming less obliquely wedge-shaped dis- 

 tally, and slightly longer, though even the terminal joints have oblique 

 ends and are scarcely, if any, longer than broad. 



Proximal pinnules much elongated, though not especially enlarged, and 

 flagellate, occasionally somewliat stiffened l)asally, with twenty-five or 

 more joints, squarish or slightly longer tlian l)road ; I'l always shorter and 

 more slender than Pj, the latter being less than, equal to, or longer than, 

 Pg ; Pj usually somewhat, occasionally very much, larger, on the outer 

 arms of each ray than on the inner ; the distal pinnules are short, never 

 so long as the elongated proximal pinnules. 



Color (in spirits). — Various shades of yellow, j'ellowish, reddish, or 

 blackish brown, or grayish to deep purple or violet, often more or less 

 mottled with darker or with yellow or white. The long lower jiinnules 

 and cirri are usually lighter than the remaining portions of the animal. 



Distribution. — Madagascar northward to the Red Sea, eastward along 

 the coasts of India, Ceylon, and northern Australia ti> tlie coast of (^hina, 

 Japan, Fiji, the Philippines, the Tonga and the Marshall Islands. 



Depth. — J.,ittoral, and extending downward to at least 28 fathoms.* 



The species referable to this genus are : 



• Chadwic'k rccorrts D. okelli from a station at wliich the recorded depth was U/^-36 

 fathoms; Carpenter records D. occulta from a dcptli of 'JIO. 2.')5, or (iio fathoms: butaddi- 

 tional conflrraation of even the lowest of these last is needed. 



