7U2 MR W. T. CALMAN ON 



and in the natural position they are turned forward so as to oppose the posterior face 

 to the corresponding part on the other side. The second joint or basipodite is very- 

 small, and carries on its outer face the exopod, which in the limb under consideration is 

 short, and indistinctly or not at all segmented. The third joint or ischium is long, 

 compressed, and thinned away toward the inner edge, which is somewhat produced and 

 fringed with setae. The basipodite is followed by Jive distinct joints, so that the main 

 axis of the limb presents one more than the normal number of seven joints. Such 

 an increase in the number of joints is not found elsewhere in the case of the maxilliped, 

 though the number seven may be exceeded in the posterior thoracic limbs from the 

 third onwards in various Mysidse. The last joint is very small, and bears a number 

 (about four) of stout curved spines. 



The succeeding limbs, while agreeing in general form with the maxillipeds, present 

 certain modifications in detail. The second pair (Plate II. fig. 13) lack the peculiar 

 internal lobes which in the maxillipeds are borne by the coxal joint. The branchial 

 lamellae are much broader, ovate in shape, and their points of attachment are close 

 together on the outer face of the coxa. The latter is very small, and partly fused with 

 the third joint, from which, however, it is marked off by a distinct line. The exopodite 

 is very large, and consists of an unjointed peduncle bearing a many-jointed, setose 

 flagellum. The ischium is cylindrical, and not produced inwards to a cutting edge, as 

 in the maxilliped. The third, fourth, and fifth pairs of thoracic limbs agree precisely 

 with the second, save that the line of demarcation between the second and third joints 

 becomes less distinct as we go backwards, while in the sixth pair the fusion of these 

 two joints is complete, and the exopod appears to spring from the ischium. In the 

 seventh pair of thoracic legs the exopod is reduced to a short unjointed lobe, and the 

 branchial lamellae are reduced in size. In the last pair of thoracic legs all these 

 appendages are wanting, and the limb is only represented by the endopodite. 



As regards the branchial lamellae or epipodites, the possession by each limb of two 

 is a most striking and important feature. In no other adult Crustacean do we meet with 

 such a character as these two separate epipodites. They are completely separate from 

 one another, and in the maxilliped a wide interval occurs between their origins. 

 Thomson has suggested that these structures may be comparable to the epipodite of the 

 Euphausiidas, which, in the course of development, is at first bifurcate, but their arrange- 

 ment in Anaspides does not suggest such a mode of origin, and it is important to note 

 that on the maxilliped (where, in Anaspides, the two epipodites are most widely 

 separate) the epipodite in the Euphausiidse is always simple, it being branched only on 

 the posterior limbs. There is, however, another possibility that suggests itself in con- 

 nection with these epipodites. Claus has shown* that in the larvae of certain Penseidse, 

 not only the podobranchiae, but also the arthro- and pleurobranchiae develop as out- 

 growths from the first joint of the legs, and he is inclined to regard the possession of 

 three epipodial appendages as a primitive, if not primary, feature of the Malacostracan 



* iVeue Beitr. z. Morph. d. Crust., Arb. Zool. Inst. Wien, vi., 1886, pp. 42-45. 



