OCR Text |
Show 50 MR. E. J. MIERS ON CRUSTACEA FROM [Jan. 14, with a distinct postfrontal and lateral suture, besides two smaller and less distinct sutures on the sides towards the lateral margins. The median frontal lobe is broadly triangulate and rounded at apex. The first postabdominal segment is very small, the five following subequal, with the lateral margins straight, the last small, transparent, and membranaceous in its distal half, and ciliated on its margins, the terminal median notch very small. The ocular peduncles are a little shorter than the frontal margin, and are furnished with very small scales at base. The corneae are of a red-brown colour. The antennules are half as long again as the eye-peduncles, the antennae about as long as the antennules; the aciculum at base very small, acute, not half as long as the eye-peduncles. The anterior legs are much as in Cancellus; the arms with a slight denticulated crest on their upper surface, the wrists very short and slightly denticulated above; the flattened upper surface of the palms is covered with thick short hair, the surface beneath being smooth, and the straight inner and arcuate outer margins very slightly denticulated. The slender and elongated legs of the second and third pairs have the antepenultimate joint short, the two following long and straight, the last in particular very long, slender, and acute. The truncated distal end of the last joint of the fourth leg is armed with a series of short stiff setae or spinules, and a small claw or spine; that of the fifth pair is densely ciliated. The basal portion of the uropoda is short and broad, and bears two unequal lamelliform rami, which are of spongy texture on the outer surface, and ciliated on the margins; the outer is twice as long as the inner. Length 5 lines. Two specimens were collected, inhabiting a species of Dentalium, at a depth of 58 fathoms, in lat. 32° 43' N., long. 129° 28' E., preserved in spirit. They were so firmly ensconced in the narrow conical shell that forms their home, that the one from which the foregoing description was mainly taken could not be extracted without breaking the shell. The chelae of the anterior legs, meeting above the head, and in close contact along their flat inner margins, form a perfect operculum, fitting the aperture of the shell (hence the name of the genus), serving to defend its inhabitant against foreign intruders. Subsequently two other specimens, in a dry state, were extracted from specimens of Dentalium, collected in 48 fathoms, in lat. 34° 13' N., long. 136° 37' E. They appear to be males, as the genital apertures are visible at the base of the fifth legs. This remarkable form is of great interest as apparently establishing a transition from the Paguridea to the Macrura. In the form of the carapace, eyes, antennae, and cephalothoracic limbs it has so much affinity with Cancellus, that, had the rest of the animal been wanting, I should have considered it a species of that genus. But in the narrow, straight, and distinctly-segmented postabdomen, and in the form of its appendages, it far more nearly approaches the Macrura than does Cancellus. Perhaps its nearest allies are to be found in the little-known genus Prophylax of Latreille1, and Glau- 1 In Cuv. E. A. (ed. 2), p. 78 (1829). |