1855.] SALTER HIMANTOPTERUS. 31 



wide, with a strongly serrate edge. The whole surface is orna- 

 mented with scale-like sculpture. The hypostome, or anterior part 

 of the under side of the head, is transverse, and from beneath it 

 spring the linear but rather broad antennae, which are considerably 

 longer than the carapace. 



The swimming-feet are formed of six joints, the basal or coxal 

 joint very large ; a second, third, and fourth of irregular shape ; the 

 angle of the bent limb being formed by the third (rather than the 

 fourth, as in H. acuminatus) ; and the fifth and sixth are elon- 

 gated, but not much wider than the rest ; the penultimate joint is 

 the larger of the two, and is notched to receive the terminal ovate 

 palette. These swimming-feet always start exactly from the angle 

 of the carapace, where it joins the first body-ring ; and we are able 

 hence to ascertain the true hinder edge of the carapace when it is 

 otherwise obscured by pressure. 



There are some flat appendages, of a cordate-ovate form, which 

 are frequently associated with this species, but their nature is wholly 

 unknown. It is possible they may be scale-like appendages at the 

 base of the antennae. One is figured in the woodcut (fig. 7). 



4. H. PERORNATUS, sp. uov. Fig. 6. 



H. magnus, pedalis et ultra 4 uncias latus ; capita sublaevi ; thorace valde 

 sculpto, et ex segmentis 6 latissimis curvatis composito; segmento 

 primo angusto lateribus rotundatis, secundo subfalcato, reliquis sub- 

 parallelis ; segmentis omnibus antice squamulis minutis omatis, postice 

 sublsevibus j angulis capitis acutis ; oculis anticis (minoribus ?) granu- 

 latis. 



Of all our specimens this one only shows the true consistence of 

 the corneous crust, and the slight general convexity, which, it is 

 probable, all the species possessed. The head is fully half a broad 

 oval, and has the eyes rather forward, but small (in proportion to 

 those of H. bilobus), and these show the lenses well. 



The head is smooth, or at least shows none of the peculiar sculp- 

 ture so visible on the thorax-rings ; and these only show it on the 

 anterior half and on the sides, the posterior half of each segment 

 being smooth. The sculpture consists of short scaly markings, 

 directed backwards like those of Pterygotus, but far smaller ; and 

 these are very prominent, though of small size, and rather irregular 

 as to the amount of curvature. They are very like those on the 

 Eurypterus figured by Eichwald, and above referred to. Probably 

 this sculpture is characteristic of the whole family of the Eury- 

 pteridcB. 



The fulcral point of these wide body-segments (fig. 6) is very near 

 (f ths of an inch in a segment 4 inches broad) to their ends, and the 

 forward curve of the segment is changed at this point for a straight 

 outward direction. One of these pleurse, broken out from the specimen, 

 showed that there was an incurved sculptured portion for a short 

 distance on the under side, like that of the Trilobite. 



