142 



BRITISH FOSSIL CRUSTACEA. 



however, been met with in Pteryyotus (page GO), and in Slimonia (p. 112). There 

 are at least eight articulations in the antennules, but I cannot positively discern a 

 ninth. 



The lateral lobes of the thoracic plate in the individual of this species originally 

 described by us and figured on PI. XXVIII, fig. 2, and 2 a are much deeper, in propor- 

 tion to the pair of median appendages, and the two intercalated plates are larger than in 

 the American Eurypteri. 



Fig. 44 



Fig. 44. — Diagram-figure of Eurypterus lanceolatus, Salter, restored chiefly from 

 fig. 2, PI. XXVIII. The endognaths are given upon the authority of Mr. 

 Robert Slimon, of Lesmahagow, Lanarkshire. 



1. The dorsal aspect of the body. 2. The ventral aspect of the body — a, the 

 antennae ; b, c, d, the endognaths ; e, the ectognaths ; t, t, the thoracic plate, 

 or operculum. 3. One of the antenna? enlarged, from a detached example 

 found by Mr. Sliraon. 



1 — 12, body-segments ; 13, telson. (See ' Geol. Mag.,' 1864, vol. i, p. 107, pi. v, 

 figs. 7, 8, 9.) 



In fig. 1, PI. XXVIII, however, there is evidence of a much longer median 

 appendage, seen as an impression lying beneath the 9th, 10th, and 11th segments, and 

 probably not less than 8 lines in length. It is highly probable, as stated elsewhere (see 

 ante, pp. 114 — 118), that this variation in the form of the central appendage is a sexual, 

 and not a specific, character. 



