﻿PTERYGOTUS GIGAS. 83 



ments only are yet found ; the large base of the fixed claw is about five inches long to 

 the first tooth (in the largest P. anglicus it is not more than three inches and a quarter)* 

 and one inch ten lines broad (nearly of equal breadth throughout). The articulating 

 edge is long and oblique, the joint narrowing considerably into the serrate claw. Of 

 this portion there is but little preserved, but it shows the chela to have had broad 

 (probably subovate) cutting teeth, as well as numerous close-set smaller ones. These last 

 are short, conical near the base of the fixed claw, and coarsely striated parallel to their 

 sides, the striae branching from above downwards. Further out (as shown in the specimen, 

 fig. 2, op. cit., which may be the free claw), the smaller teeth are lanceolate and narrow, 

 and the striae parallel. These striae are very closely set, much more so than in any other 

 species. The teeth appear to have been irregular in size, and much crowded ; a third 

 specimen (fig. 3) shows three kinds, a small lanceolate one, larger subovate secondary ones, 

 and one a great striate tooth, apparently the median one (see pi. vi, fig. 5, op. cit.), 

 which is coarsely ribbed, and is, besides, serrated on the inner edge. 



The endognath has somewhat broader and shorter teeth than that figured in pi. vii 

 (op. cit.), and the second maxillary piece is more curved anteriorly. Both specimens are 

 preserved in Mr. Banks' cabinet. 



Of the palpi (pi. ix, figs. 5 — 7, Mem. Geol. Surv., Mon. I) only fragments are left. Fig. 5 

 shows four joints connected, but all compressed in a direction perpendicular to their length.' 

 Their diameter is half an inch, and their proportions may be compared with those shown 

 in pi. vii, fig. 4 (op. cit.). The second joint is rather longer, and the third not quite so 

 long as in P. anglicus. The other figured fragments are less distorted ; fig. 6 shows the 

 fourth joint fully one inch and a half long, with the tip expanded and bilobed. In fig. 7 

 one of the lobes bears a fringe of spines. All the joints show elongate squamae on their 

 outer side. 



Swimming -foot (pi. ix, figs. 4 — 9, Mem. Geol. Surv., Mon. I). The great basal joint 

 (fig. 8), with its serrated tip, closely resembles in form and sculpture that figured in pi. vii, 

 ' Geol. Surv. Mon./ the chief difference being the greater width of the foliaceous base, and 

 the more backward position of the notch at the point of attachment for the succeeding 

 joints. The serrate terminal lobe (figs. 4 and 9) has broad stout teeth, as usual, thirteen 

 in number, slightly curved, the uppermost broader and shorter than the rest, the lowest 

 a rounded lobe as broad as the two preceding teeth taken together. The teeth are 

 shorter than in P. anglicus, especially the upper ones, so that the outline of the serrate 

 edge is more curved. The perfect specimen is only three inches and a half long by two 

 inches and three quarters broad, but fragments indicate a size equal to the largest speci- 

 mens of the Scotch species. 



Of the other joints of the swimming-foot only two or three specimens (pi ix, figs. 

 10 — 12, Mem. Geol. Surv., Mon. I) have occurred. Fig. 10 shows the upper surface of 

 the right-hand swimming-foot, with two complete joints ; the fourth and fifth, with a portion 

 of the great penultimate joint. The latter joint is better shown in another fragment 



