204 BULLETIN OF THE 
and arrangement. Narrow at the base, each joint expands so as to be 
of a subtriangular outline in a cross section, with the exception of the 
basal joint which is broader at the base, narrowing towards the outer 
extremity. By a comparison of the longitudinal section of the basal 
joint in Calymene, Plate V. figs. 1 and 3, with the transverse section, 
Plate III. fig. 9, it is seen that this joint was transversely flattened. 
The means of such a comparison in Ceraurus are not as good, although 
the somewhat distorted basal joint, Plate II. fig. 6, may be placed with 
those of Fig. 8, and compared with the transverse section of the 
basal joint, right side, of Fig. 3. Fig. 3, Plate IIL, is a fine illustra- 
tion of a section cutting across the basal joints of the thoracic legs at 
different points, as they are brought into the line of the section by the 
enrolment of the animal. The terminal joint of the leg has not been 
recognized as such in either species, which makes it difficult to say 
how many joints there are in the legs. Six isthe usual number in the 
sections, but in one there is seven, if the evidence of Fig. 2, Plate IT, 
is to be relied upon. 
The character of the appendages beneath the pygidium is one of 
unusual interest, and for a long time was highly problematical, and at 
present the evidence is not all that could be desired. Four sections, 
two transverse and two longitudinal, show their presence in Ceraurus. 
That they are jointed is shown by Plate II. fig. 8, and also in a similar 
section not illustrated. The transverse section, Plate II. fig. 4, of the 
extreme posterior segment of the pygidium also shows the base of the 
leg and sections of the succeeding anterior legs. The position of 
the base is the same as that of the posterior leg, Plate II. fig. 8. 
That these legs were not foliaceous and branchial is evident, but what 
their terminal joints were like is yet an unsettled problem of the 
investigation. 
With Calymene the success in cutting a section so as to show all 
the joints of the leg has not been as good as for Cerawrus. The 
knowledge of its structure is based on a number of fragmentary parts 
after the third joint from the base is passed. Plate V. figs. 1, 3, and 4, 
give a fine illustration of the first three joints. A transverse section 
obliquely crossing an enrolled specimen cuts across the legs as they 
diverge from the anterior extremity of the thorax. Each pair of legs 
is cut across farther from the base, so that we have an approximate 
outline of their form, which, from a comparison of the parts as seen in 
many sections, resemble those illustrated on Plate VI. fig. 5, while those 
of Ceraurus are more like those of Fig. 4 of the same plate. 
