REPORT ON THE PHYLLOCARIDA. 11 



oil of cloves, and then mounting it in Canada balsam, I have succeeded in rendering the 

 whole body sufficiently pellucid to admit a closer examination of the several parts in 

 their natural connection with each other (see PI. I. fig. 1). 



As to the external appearance (see PI. I. fig. 1; PI. IL fig. 1) the present form 

 exhibits on the whole a great resemblance to the common species of Nehalia, with this 

 exception, however, that the terminal part of the body, comprising the four last segments, 

 is comparatively more slender and also more distinctly marked off from the preceding 

 part than is the case in Nehalia. In describing the body I find it advisable to 

 distinguish four principal divisions, viz., the cephahc part, to which the carapace is 

 connected, the trunk, the pleon, and the urosome or tail, the two latter parts answering 

 to the so-called abdomen in the higher Crustacea, and to the abdomen and thorax in the 

 Copepoda. All these four divisions are pretty well defined in the present form, and are 

 of about equal length, but differ both in form and in the structure of their respective 

 limbs. 



The cephalic part is somewhat flattened, and along its whole dorsal surface firmly 

 connected with the carapace. It bears the following appendages, enumerated from before 

 backward.s : — The eyes, the antennulse, the antennje, the anterior lip, the mandibles, 

 the posterior lip, the first pair of maxiUse, and the second pair of maxillae. Of these 

 appendages only the eyes, the antennulse, and the antennae project to a certain extent 

 beyond the free edges of the carapace, all the other parts being wholly concealed within 

 its valves. 



The trunk is almost cylindrical in form, and only slightly longer than broad. It is 

 composed of eight short segments, well defined in their whole cii'cumference, and nearly 

 equal in size, each bearing a pair of branchial legs, the outer part of which projects, 

 beyond the free edges of the carapace. 



The pleon is at the base fully as broad as the trunk, but tapers gradually, so as 

 scarcely to be more than half as broad at the end. It is composed of four well-defined 

 segments, each bearing a pair of powerfully developed natatory appendages or pleopoda. 

 The last segment is provided with distinct, rounded, cpimeral plates, partly covering the 

 base of the corresponding pair of pleopoda. 



The urosome or tail is rather slender, and very movably connected with the pleon, so 

 as often to form an angular bend with it (see PI. I. fig. 1). It is nearly cylindrical in 

 form, and composed of four segments, the first of which is the smallest, and, properly 

 speaking, corresponds to the last thoracic segment in the Copepoda. This and the suc- 

 ceeding segment bear each a pair of rudimentary caudal limbs, whereas the third segment 

 is without any trace of limbs. The last segment terminates in two slender, diverging 

 branches, evidently answering to the so-called " furca " in the Copepoda, and to the 

 caudal lamellae in the Brauchipodidaj. The two middle segments of this division are 

 denticulate at the posterior edge, and the last segment projects at the end, beneath the 



