92 NEW YORK STATE MUSEUM 



The posterior portion of a smooth cephalothorax that mlay very 

 well have belonged to the same species was also found in the plant 

 beds that have afforded the smaller specimen. This small indi- 

 vidual may also belong to the same species. At least the outline of 

 the cephalothorax and of the postabdomen, as well as the sub- 

 marginal position of the supposed compound eye, suggest its refer- 

 ence to Pterygotus, although the specimen is not sufficiently perfect 

 to give conclusive evidence as to either its generic relation or relative 

 age. The cephalothorax is narrower than in the adult age, but 

 possibly so to some degree by lateral compression. The preabdonien 

 retains only one or two segments, the first of which is pushed under 

 the cephalothorax, and the postabdomen has been pushed forward 

 into the preabdomen, giving the body an altogether too short out- 

 line. Traces of relatively weak and narrow swintming legs, such as 

 are possessed by Pterygotus are seen close to the sides of the body. 



6 Preservation of Alimentary Canal in an Eurypterid 



A small series of eurypterids from the Silurian waterlime at 

 Kokomo, Ind., bought some years ago from Ward's Natural Science 

 Establishment, contains a specimen of Eusarcus newlini 

 Claypole, that is worth noting for two reasons ; first, it is a younger 

 individual than has hitherto been observed and "exhibits certain 

 adolescent features ; and second, it retains the alimentary canal ; to 

 the writer's knowledge, not before observed, or described, at least. 

 in any eurypterid. 



The specimen is but 142 mm long, or one-fourth the size of the 

 large specimen figured by Clarke and Ruedemann (The Eurypterida 

 of New York, 1912, on pi. 39). In its relative dimensions it cor- 

 roborates the view expressed before (ibid., p. 252) that the mature 

 individuals had a more robust and less agile appearance ; for this 

 young individual is distinguished from the supposedly mature form 

 by a relatively more slender body, a more elongate carapace, less 

 broadly expanded preabdomen and relatively longer postabdomen. 

 The legs are distinctly more slender, though not relatively longer. 

 The eyes which are placed terminally in front, are more prominent 

 than in the later stages though not any more relatively larger. 



The alimentary canal is traceable through the greater part of its 

 length. It is seen from the dorsal side, beginning in the middle of 

 the carapace with an expanded portion 8 mm long and 5 mm wide 

 and extends thither as a perfectly straight tube, with a nearly uni- 

 form width of 3.5 mm to within 3 mm of the posterior edge of the 

 last postabdominal segment, where it abruptly disappears. 



