C. E. Beecher — Restoration of Stylonurus Lacoanus. 149 



The chelate antennae were doubtless carried in a folded posi- 

 tion, as in most related genera, and seldom were visible from 

 the dorsal side. They are, therefore, not shown. The three 

 pairs of short gnathopods, serving partly as swimming organs, 

 are seen extending outward from the anterolateral margins of 

 the cephalothorax. Several of their distal joints are each pro- 

 vided with a pair of flat, ridged, spinous processes, and a 

 similar spine at the termination of the limb. 



The two pairs of great crawling feet extend outward and 

 backward from the postero-lateral margins of the cephalo- 

 thorax. The anterior pair expose 109 cm of length, and the 

 posterior pair about 108 cm . The elements of the limbs are 

 represented as grooved, as this character seems necessary to 

 give the needed strength to long slender joints, and also 

 because a similar conformation is present in S. Beeoheri. 



The abdomen measures 30 cm in greatest width at the fifth 

 segment, and 66 cm in length exclusive of the telson. The pos- 

 terior abdominal segments are represented without detachable 

 epimera, as this feature is not as yet known to be constant for 

 the genus, although present in some species. 



The telson spine agrees proportionally in length with the 

 same member in S. Logani and S. Powriei as described by 

 Woodward, 10 and was given a slight upward curvature as in 

 Limulus. It measures 54 cm in length and 7'5 cm across at the 

 proximal end. 



Altogether the animal as restored has a length of nearly five 

 feet (147 om ), and with the legs extended it would measure 

 about eight feet (242 cm ) across. 



It is not intended to claim any high degree of accuracy for 

 this restoration, but merely to represent in some graphic form 

 an animal approximating in size and character an individual of 

 the species Stylonurus Lacoanus. Its size alone was the chief 

 incentive for attempting a reconstruction, and some sacrifice of 

 exact detail may well be allowed, in order to make any presen- 

 tation of this magnificent arthropod. 



Yale University Museum, New Haven, Conn., September 5, 1899. 



References. 



1. Claypole, E. W. — Note on a large Crustacean from the Catskill Group 

 of Pennsylvania. Proc. Amer. Phil. Soc, vol. xxi, April, 1883-January, 

 1884. 



2. Dawson, J. W. — Notes on New Erian (Devonian) Plants. Quar. Jour. 

 Geol. Soc, London, vol. xxxvii, 1881. 



3. Hall, J. — Description of a New Species of Stylonurus from the Catskill 

 Group. Thirty-sixth Ann. Eept. N. Y. State Mus. Nat. Hist., 1884. 



4. Hall, J. — Note on the Eurypteridae of the Devonian and Carboniferous 

 Formations of Pennsylvania. Second Geol. Surv. Penn., PPP, 1884. 



5. Hall, J. — Note to Explanation of Plate 15 of paper on Geology of 

 Yates County, N. Y., by B. H. Wright. Thirty-fifth Ann. Eept. N. Y. 

 State Mus. Nat. Hist., published 1884. 



