76 BRITISH FOSSILS. 



b. The second joint (basignathite) is transverse, more than twice 

 as wide as long, and furnished anteriorly with a large rounded boss 

 occupying the exterior third of the joint (see fig. 2), broken off from 

 the limb and left attached to the coxal segment in fig. 1 at 6*. Its 

 hinder articulating border is somewhat concave, its inferior angle 

 rounded and produced. 



i. The following joint is subtrigonal with rounded sides on the 

 upper surface, and with an obtuse angle projecting over the centre 

 of the following joint, but on the under surface it is rhomboidal, 

 more than twice as wide as long, and with the distal and proximal 

 edges nearly parallel (ischygnathite.) 



m. The fourth joint is trigonal, the outer edges wide, convex, 

 and forming the angle of the limb, terminating in a rounded process 

 extending half way down the following joint. On the upper side, 

 fig. 1, the distal articulating edge is produced ; on the under side, 

 fig. 2, deeply emarginate to receive a process from the fifth joint 

 c a. The inner side of this joint (merognathite\ which is rather 

 a difficult one to describe, is much narrowed, and terminates in an 

 acute angle opposed to the wide basis of the outer margin. 



c a. Of the next joint (carpognathite] it is equally difficult to give 

 a clear idea ; its shape is irregular. It is somewhat crescentic on the 

 upper surface, its outer side much the longer, and its distal margin 

 oblique, nearly straight for the greater part of its length, but the 

 outer angle truncated, and the inner notched. On the under side it 

 follows the shape of the preceding joint, and has a prominent 

 median process above to fit into the notch of it. Its distal margin, 

 too, on this surface is sinuous, and less oblique than on the upper side. 



p. (and fig. 3.) The penultimate joint (prognathite) is flattened (to 

 form with the last, d, a swimming palette.) Our largest specimen 

 measures two and a half inches in length, by one and a half at its 

 broadest part. It is somewhat quadrangular, but one-third broader 

 below than above. Its outer edge is perfectly straight, longer than 

 the inner, and terminating above as a narrow rounded lobe, behind 

 which is a deep emargination, continuous with the curved outline of 

 the inner margin. The latter is produced inferiorly into a subtri- 

 angular lobe (3 c), broader than the superior process of the outer 

 margin above described. The rest of the inferior border (d) is 

 nearly straight, and forms almost a right angle with the straight 

 outer margin. 



d. The terminal palette (dactylognaihite) is broadly ovate, twice as 

 long as broad, its apex rounded, its outer margin quite regular ; the 

 inner a little flattened above, leaving room for the play of the 

 palette against the penultimate joint, as in the swimming crabs. 



