PLATE IX. [Pate 20.] 
SecTIon 2,—PTER YGOTUS. 
Pterygotus gigas. APPENDAGES, &C. 
Fig. 1. The swelled base of the antennary chela ; two-thirds of the natural size. 
Fig. 2. Another specimen, showing the crowded teeth. 
Fig. 3. The free ramus of a chela, with the great serrated tooth, ¢ ; the smaller primary teeth, 
6; and the secondaries, «. (See Plate XII. Fig. 9*.) 
. Part of the serrated lobe of the ectognath. 
. Four joints from the proximal end of an endognathary palpus, shortened by pressure. 
4 
5 
Fig. 6. The third joint of an endognathary palpus, showing its bilobed distal end. 
7. The fourth (?) joint, exhibiting its crested distal termination. 
8. The basal lobe of an ectognath, the serrated lobe imperfect. 
9. Part of the serrated process of a larger specimen. 
Figs. 10 and 12, Joints of the ectognath or swimming foot. 12. The fourth and fifth joints, 
with part of the penultimate joint, * 10. Penultimate joint, A*, imperfect. 
Fig. 11 is the distal trilobed end of the penultimate joint. 
Fig. 13. Anterior end of the sternal surface of the metastoma or post-oral plate. 
Fig. 14. Problematical bodies, frequently occurring with this species. The surface when 
perfect is tessellated as at a, but not regularly so. 
Fig. 15. Sternal surface of the eleventh segment of the body. The short anal (?) ridge at a. 
Two-thirds of the natural size. 
Fig. 15a. Tergal surface of the same segment (compare with Plate VIII. Fig. 7), reduced to 
two-thirds of the natural size. 
Fig. 16. A large caudal joint (telson) with its median crest, seen in profile at 16¢. A portion 
of the crest, distorted, is shown at 16a, and Fig. 16 ¢ exhibits a restoration of its 
original form. 
Fi 
Fi 
g. 17. One half of the sternal surface of another telson. (Mr. Lightbody’s collection. ) 
g. 18. A telson (possibly of P. /udenszs); two-thirds of the natural size. From the base 
of the Old Red Sandstone, Ludlow Railway. (Museum of Practical Geology.) 
— 
The above, except Fig. 18, are from the Downton Sandstone (Upper Ludlow 
Rock) at Kington, Herefordshire, and all are in Mr. Richard Banks’ cabinet, unless it be 
otherwise stated. 
