THE EURYPTERIDA OF NEW YORK 381 
Salter and P. banksii Salter and also those of H. socialis.” 
The reference to Hughmilleria in this connection appears to us especially 
significant, since the eyes show the distinct angulation on the inner side, 
so characteristic of that genus, and moreover fail to exhibit any 
signs of the facets, generally quite distinct in Pterygotus. It is quite 
possible that this specimen is a very large carapace of Hughmilleria 
partly doubled upon itself in front (of which there is evidence along a 
break); although on the other hand it must be conceded that the lateral 
eye is relatively larger than that of H. socialis. 
So far then as concerns this carapace P. monroensis is an un- 
certain species, but unmistakable evidence of the presence of a true Ptery- 
gotus in the Pittsford shale is afforded by the free ramus of a chela,' repro- 
duced in plate 70, figure 3. Sarle has separated this and a metastoma? 
[pl. 70, fig. 4] on the ground that they belong to coarse-scaled fragments 
that represent another species. Inasmuch as the carapace as a rule has a 
much finer sculpturing than the rest of the body (e. g.in P. macroph- 
thalmus), there seems little ground to assume the presence of more 
than one species of Pterygotus in the Pittsford beds. 
Judging from the ramus of the chelicera, this type was more closely 
related to P. cobbi than to any other form, the latter species possess- 
ing the same rounding of the extremity of the ramus and similar form 
and direction of the teeth [pl. 77, fig. 6], the latter being still a little 
more rectangular wpon the shaft than in P. cobbi. 
1 Sarle’s description ~f this reads: 
The shaft is nearly parallel sided,3 mm broad and 12.5 mm long and curves 
at the end into a stout, striated, nearly..perpendicular.mucro 3.5; mm long. Back 
of this mucro is a series of ro erect, subtriangular, striated denticles, very slightly sepa- 
rated at their bases. They are of three sizes, the largest or primaries being about one 
half the length of the mucro, the secondaries.-one-half that of the primaries and the 
tertiaries about one half that of the secondaries. The first primary is separated from the 
mucro by a secondary and from the second primary by two secondaries and two tertiaries 
alternating; following the second primary are two secondaries separated by a tertiary. - 
? Described as follows: An ovate metastoma 27 mm long and 16 mm wide, broad- 
est just anterior to the middle, with the anterior corners slightly truncated, the lobes 
small and the terminal notch very narrow and shallow. It is marked by coarse, rounded, 
lobelike scales and is very much more robust than would be expected in Pterygotus 
monroensis. Judging by the ornamentation, it should be associated with the coarse- 
scaled fragments most frequently found. : 
