416 * 
PALAEONTOLOGY OF NEW-YORK. 
Genus PterygOTUS (Agassiz). 
This genus was established by Prof. Agassiz in 1844, in his “Monographic 
des poissons fossiles du vieux gres rouge”. The specimens then known 
were all fragmentary; and although some additional facts were from time 
to time obtained, it was not until 1856 that Mr. Salter published* an 
illustration of the restored form of the animal, under the name Himan- 
topterus, which he subsequently determined to be identical with Ptery- 
gotus. 
The form is very similar to Eurypterus; the eyes being marginal in¬ 
stead of within the carapace, while the caudal extremity is bilobatef. 
The number of segments of the body, as represented, is one less than in 
Eurypterus; but this may have arisen from observing the lower side only, 
and the suture, if existing as in Eurypterus, may not have indicated a 
separate articulation. One other remarkable difference between this genus 
and Eurypterus is in the “ chelate antennae ” placed at the anterior part of 
the carapace ; a relation which seems scarcely credible, but for the au¬ 
thority under which it is presented. 
A fragment, the free ramus of one of the chelate antennsej of a species 
of this genus, has been found near Buffalo by Mr. Cobb ; and in the same 
collection with it there is a single joint, apparently a caudal joint, which 
differs from any similar part of Eurypterus known to me at this time. 
* On some new Crustacea from the uppermost Silurian rocks, by J. W. Salter, F.G.S.; with a Note on 
the structure and affinities of Himantopterus, by T. H. Huxley, F.G.S. ( Quarterly Journal of the Geo¬ 
logical Society, Vol. xii, p. 26.) 
f The spiniform caudal appendages, figured on the same page as belonging to this genus, may prove to 
be Eurypterus. 
J Chelate antennae of Huxley and Salter. Notwithstanding that these organs are placed at the anterior 
part of the carapace, and in the position of antennae, the similarity of structure in Pterygotus and Eury¬ 
pterus induces me to believe that other relations of these parts will yet be found; and that chelate an¬ 
tennae of this character, and in this position, do not belong to Pterygotus; or else that we have misunder¬ 
stood the specimens referred to this genus among our collections. The many structural analogies between 
these crustaceans and Limulus would induce me to regard these organs as analogous in some measure with 
the chelate antennae [palpi] of that animal, and as having a similar position anterior to the mouth. 
