CANCER, a genus of Short-Tailed Crustacea, the type of the family Canceri&e. Dr. Leach restricted the genus Cancer to the form of ,Cancer Pagurus, Linn., the large eatable Crab of our coasts, which was, when he defined the genus, the only species known. It has tho following characters : External antennae with the basilar joint broad, very long and thick, filling the hiatus between the inner canthus of the orbit and the front, and terminating forwards in a strong, angular, tooth-like projection, directed forwards and a little inwards, reaching beyond the frontal line. The terminal or moveable portion is slender, very short, and arises from the internal part of the basilar joint nearer to the cell of the internal antennae than to the orbit. The internal antennae, instead of lying obliquely outwards or transversely, as in most other genera of this section, aro directed forwards—a character by which Cancer may at once be distinguished from Platypodia, Carpileus, Xantho, &c. The second joint of the inner footatalk of the external pedipalps is excavated at the anterior part of the inner margin ; in some species the notch is confined to the angle, in others it extends half way down the side of the joint. The first pair of feet is nearly equal ; in some specimens of each species the difference in size being scarcely appre ciable. They are generally very robust. The remaining feet have no spines, but are iu most species more or less hairy. The abdomen of the male has five, and that of the female seven joints.
With the exception of our indigenous species, Cancer Pagurus, they are all, as far as their localities are known, exclusively natives of tho coasts of the hotter parts of America.
Mr. Bell, in a paper on the genus Cancer (` ZooL Trans.' i. 335), gives three new species, namely, C. longepes, C. Edwardsii, and C. dentatus, brought home by Mr. Cuming and Mr. Miller, besides C. irroratus of Say, and C. Pagurus, which last, as it was considered the typo by Dr. Leach, we select as an example.
C. Pagurus is the Great Crab of the English coasts. Mr. Bell gives the following description of it :—Carapace transversely oblong, flattened, but little higher in the middle than at the sides, some what rounded before and behind; the surface minutely granulated, smooth, with the regions but slightly marked. Latero-anterior
margin slightly recurved, divided into ten quadrate lobes, the sides of which are contiguous and the margins entire; the last lobo inconspicuous, and passing into the posterior marginal line, which terminates immediately anterior to the posterior transverse ridge. Front trifid, the teeth of nearly equal length and size. Orbits round, with a strong triangular tooth over the inner canthus, which does not project so far as the front; and a smaller one filling the space between the two superior fissures. External antennae with the basilar joint much elongated, and terminating forwards in an obtuse tooth ; the first joint of the moveable portion club-shaped, the second cylindrical, the remaining portion setaceous. Internal antennee directed forwards, the anterior half doubled directly back wards in a state of rest. The basilar joint broad, cup-shaped, its outer edge projecting forwards; the second joint (the first of the moveable portion) cylindrical, the penultimate with a small, hooked, and recurved process at the apex. Padipalps as in the rest of the genus. Sternum minutely puuctated, and furnished with small patches or lines of short scanty hair. Abdomen iu the male with the margin fringed with short hair ; the last joint forming an equilateral triangle. Anterior feet large, robust, smooth, without spines or tubercles, minutely granulated ; the hand rounded, without crest, the inner surface exhibiting only the rudiments of the five lines of pnncta, so conspicuous in other species of the genus. The remaining feet furnished with numerous faseiculi of stiff hairs, the last joint in all furrowed, and terminated by a short strong nail. Colour above reddish-brown, the legs more red, the claws deep shilling black ; beneath whitish. Locality, coasts of Great Britain, &c., and of western Europe. Great numbers are annually caught on the coasts of Great Britain. They sometimes attain a large size, weighing ten or twelve pounds.