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, transpa- 

 rent, and membranaceous in its distal half, and ciliated on its mar- 

 gins, 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 cornese are of a red-brown colour. 

 The antennules are half as long again as the eye-peduncles, the an- 

 tennse 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 sHght denticulated 

 crest on their upper surface, the wrists very short and slightly denti- 

 culated 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 stiif setse 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., pre- 

 served in spirit. They were so firmly ensconced in the narrow coni- 

 cal shell that forms their home, that the one from which the fore- 

 going description was mainly taken could not be extracted without 

 breaking the shell. The chelse 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 in- 

 truders. 



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 aflSnity 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 Latreille ', and Glau- 

 1 In Cuv. E. A. (ed, 2), p. 78 (1829). 



