﻿EURYPTERUS LANCEOLATUS. 141 



In the form of the joints of the swimming-feet, in the number of the body-segments, 

 the shape of the telson and thoracic plate, it closely agrees with the American, and, so 

 far as is known, with the Russian, species of Eurypterus ; but the carapace is more 

 oblong-ovate vertically, whilst that of the American species is much broader and shorter 

 in proportion. The eyes in E. lanceolatus are placed much nearer to the margin of the 

 carapace than in other species ; the swimming-feet are longer and narrower, and the 

 thoracic plate seems deeper in proportion to its width, compared with Prof. James 

 Hall's figures of the American E. remipes (see ante, Eig. 40, p. 132), &c. This is not 

 absolutely the case, however; but is, I believe, due in a great degree to the fact that 

 in Prof. Hall's restoration the broad basal joints of the swimming-feet and part of 

 the post-oral plate are placed considerably beyond the posterior margin of the carapace, so 

 that they overlap nearly one half of the thoracic plate, a position which seems highly 

 improbable, if not absolutely impossible, for them to have occupied during life, and in 

 which they never occur in any examples that I have seen of the closely allied Pteryyoti 

 from Lesmahagow, many of which have these parts united and well preserved. 



A single antennule discovered by Mr. Slimon shows these appendages to have eight 

 articulations ; the broad basal joint is serrated along its inner margin, and evidently served 

 the purpose of a manducatory organ. The three succeeding pairs are serrated along 

 their articulations, but are not quite so spinose as in the American species. The metas- 

 toma, or post-oral plate, is cordiform and quite destitute of any median ridge or ornamen- 

 tation. Its lateral margin slightly overlaps the anterior margins of the broad basal joints 

 of the swimming-feet, whose serrated palpi fulfil, in this as in all the other species of 

 Eurypferida, the chief duty of manducation. 



A slight groove or furrow surrounds the anterior and antero-lateral margins of the 

 carapace, gradually thinning off and disappearing at the latero-posterior margins. In his 

 ' Palaeontology of New York' (1859, vol. iii, p. 397), Prof. Hall gives the number of 

 articulations in the swimming-feet of Eurypterus as " eight, with a terminal palette." Pie 

 evidently considers the intercalated plate to form a part of the seventh segment, for he 

 says (op. cit.j p. 397), " At the line s there is a soldered suture, connecting the fixed ramus 

 of the chela with the penultimate joint." In the specimen from Lesmahagow I have been 

 unable to discern more than seven articulations and a terminal palette. The third appears 

 to be the absent joint. Prof. Hall says (p. 397), " In indicating the number of 

 joints, I have been governed by no theoretical views, but simply by the appearances of 

 separation in the parts ; and though the two extremities of the third joint, as marked, 

 show no articulating processes, the limitation of the parts is distinct, and they may have 

 been separated only by a thin extension of the chitine, and may not be properly articu- 

 lating surfaces." Supposing, then, this third joint of Prof. Hall's to be absent, we 

 shall agree exactly in the number of articulations in the swimming-feet as well as in their 

 general form. The intercalated plate and minute terminal palette are well seen in E. 

 lanceolatus, and were formerly believed to be peculiar to the genus. They have since, 



