[Illustration: Fig. 14.--Slice through the hypostoma and thorax of _Calymene senaria_ Conrad, showing the small size of the coxopodites nearest the hypostoma. Shell in black, appendages and filling of abdominal cavity dotted. From a photographic enlargement. Specimen 40. × 3.8.] [Illustration: Fig. 15.--Transverse section of _Calymene_, showing method of articulation with the appendifer. The shell is in solid black, the filling of the appendage and appendifer stippled. Traced from a photographic enlargement of the slice. Specimen 63. × 7.] _Exopodites._--Walcott admits that there is no direct evidence of spiral exopodites in the cephalon of _Calymene_. No one of the sections cutting through the plane of the hypostoma shows any trace of appendages which could be interpreted as exopodites. _Thoracic Appendages._ The large coxopodites of the anterior thoracic appendages are well shown in many specimens cut longitudinally, of which Nos. 23, 50, and 55 may be mentioned, since photographs of them have been published by Walcott (pl. 26, figs. 1-4, 1918). The endobases of all taper toward the proximal ends. Transverse slices show sections of the coxopodites which are no wider than those in longitudinal sections, indicating that they were not compressed but probably cylindrical. This is borne out by an individual (pl. 28, fig. 7, 1918) which is not a slice but an actual specimen, the body cavity of which was hollow, and, opened from above, shows the impressions of the last two coxopodites of the cephalon, and the first four of the thorax. One transverse section (No. 63, see our fig. 15) is especially valuable, as it shows the method of articulation of the coxopodites with the dorsal skeleton. Another specimen (No. 73) shows that appendifers are present in _Calymene_, and while the appendifer does not retain its original form in slice No. 63, the section does show clearly that there was a notch in the inner (upper) side of the coxopodite into which the lower end of the appendifer fitted, thus giving a firm, articulated support for the appendage. This notch appears to be slightly nearer the outer than the inner end of the coxopodite, and since it must have made a kind of ball-and-socket joint, considerable freedom of movement was allowed. The appendage must have been held in place by muscles within the coxopodite and attached to the appendifer. No slice which I have seen shows a continuous section through all the segments of an endopodite, but many, both longitudinal and transverse, show one, two, or as many as three segments. Such sections as No. 120 show that the endopodites of the thorax were slender and composed of segments of rather uniform diameter. Other sections, notably No. 83, 154, and in, show that they tapered distally, and bore small spines at the outer end of each segment.