1855.] SALTER HIMANTOPTERUS. 29 



1. HiMANTOPTERUS ACUMTNATUS, Sp. nOV. Fig. 4. 



H. pedalis et ultra, elongatus, articulis 12, quorum quinque ultimis sub- 

 quadratis, penultimo oblongo ; cauda magna, ovata, et in apiculum 

 serratum lougum producta. 



Of this fine species, which must have been nearly 2 feet long, we 

 have specimens which show the whole of the thoracic and abdo- 

 minal segments united. The former are broader than, but not 

 abruptly distinct from, those of the abdomen. They are transverse, 

 a httle produced at their posterior lateral edges, and have along the 

 middle of the dorsal line either one or two (probably one) short spines 

 projecting backwards. 



The abdominal segments are but little broader than long. The 

 penultimate, indeed, is quite as long as broad; and the terminal 

 joint, of which we have specimens 5 inches long, is contracted and 

 convex at the base, then rather suddenly expanded into an ovate 

 form, and produced into a long apiculus (fig. 4). A keel runs the 

 whole length of the segment, and the sides both of the expanded 

 portion and of the apiculus are crenate (less strongly than in our 

 figure). 



We have but little of the carapace, and cannot be sure that the 

 next described species does not belong to it. Of the limbs, there 

 are the large swimming feet, consisting of a very large basal joint 

 (coxa), and five others : the first narrow, the second irregular in 

 shape, the third, where the backward bend of the limb takes place, 

 subtriangular but rounded in front. The penultimate joint is much 

 longer than broad, and deeply bilobed at the tip ; the terminal one 

 is an ovate palette, two and a half times as long as broad. The scaly 

 sculpture occurs on all the joints of the limb. 



With these limbs lie a pair of antennae (?) of equal length. They 

 consist of about five rather inflated joints, terminated by a small 

 uncinate joint. They appear to be united at the base. 



2. H. MAxiMus, sp. nov. Fig. 3. 



H. capite fere 8 uncias longo, 5^ lato, oblongo, vix suburceolato, lateribus 

 antice contractis; fronte rotundato^ oculis magnis, oblongis, ad an- 

 gulos externos fixis ; margine antico et laterali tuberculato-erenatis. 



If we estimate the length of this species by taking the propor- 

 tionate length of the head to the body, which we find in the H. 

 bilohus (fig. 1), the entire creature must have been at least 3 feet 

 long ; or, if we suppose it to have had the same proportions as H. 

 acuminatus, which has more elongated body-joints, the case would 

 not be different. 



We have two specimens of the head, and both present the 

 same characters in the eyes, and in the rugoso-crenulate anterior 

 margin. 



