Munidopsis aspera (Henderson 1885)

“Elasmonotus asper, Henderson (PI. XIX. fig. 4).

Elasmonotus asper, Henderson, Ann. and Mag. Nat. Hist., ser. 5, vol. xvi. p. 416, 1885.

Characters. — The carapace is remarkably flattened, and the regions are not clearly defined; the surface is dotted with irregular tubercles, some of which are subacute, and the intervening spaces are finely granular. The gastric area is but slightly raised above the surrounding level, and the tubercles are prominent (some are even compound) towards the median line; the tubercles are most numerous elsewhere towards the lateral and posterior margins of the carapace, and two of large size are situated on the cardiac area, overhanging a shallow transverse groove. The rostrum is moderately narrow, and usually about twice the length of the eye-stalks, though in some male specimens it scarcely exceeds these in length; the apex is slightly upturned, and bidentate, the upper and larger of the two teeth being in most cases again subdivided; the upper surface is finely tubercular, and in some cases a few serrations are present on the lateral margins towards the apex. The lateral margin of the carapace is irregular in outline, but without any spines of importance; a small serrated lobe is present on the orbital border behind the ocular peduncle; the posterior margin is narrow and finely tuberculate.

The chelipedes are narrow and elongated, while the joints, more particularly the meri, are armed with short tubercular spines. The propodus is about three times the length of the carpus, and its upper surface bears a median row of tubercles; the fingers are not equal in length to the palm, and slightly pubescent, their opposed margins are dentate (the dentations being more strongly marked towards the apices) and a slight basal hiatus is usually present between the two. The ambulatory limbs are of moderate length, with the joints finely tubercular above; the meri are dilated, and their anterior margins are pubescent; the dactyli are short and strongly curved, with their posterior margins entire.

The eyes are freely movable, with the corneæ subglobose and terminal in position; the peduncle is slightly elongated, but not prolonged into a spine. The antennal flagellum is not equal in length to the carapace. The ischium and merus of the external maxillipedes are faintly granular externally; the outer margin of the former is prolonged distally into an acute spine, while the inner margin of the latter is irregularly dentate, and a curved acute spine is placed at the distal end and outer border of the same joint.

The second and third abdominal segments are each provided with a prominent median tubercular elevation, the surface of which is roughened, and scattered tubercles of small size are present towards the lateral margins of the same segments. The posterior segments are perfectly smooth.

Several of the distinctive features of this species are peculiar, as for instance the flattened carapace, the bidentate rostrum, the short curved ambulatory dactyli, and the median abdominal tubercles; but they are not, in my opinion, sufficient to separate it from the genus Elasmonotus. Females are apparently slightly larger than males, their rostrum is more strongly developed, and their chelipedes are shorter.

Breadth of carapace (of an adult male) 8 mm., length of body (including rostrum) 24 mm., of carapace (including rostrum) 13 mm., of chelipede 31 mm., of first ambulatory leg 18 mm. The ova measure about 1 mm. in diameter. The body of the largest female measures 29 mm. in length.

Habitat.¹ — Station 311, off Port Churruca, Patagonia; depth, 245 fathoms; bottom, blue mud. Upwards of a dozen specimens, the majority of which are females with ova.”

(Henderson. 1885)