484 Professor C. E. BeecJier — On SUjlonurus Lacoanus. 



number of real things. Some statement, therefore, should be given 

 of the character and amount of the material that has been collated to 

 furnish a restoration of Shjlonurus Lacoanus. 



(1) The specimen of the cephalothorax described by Hall shows 

 the complete outline and upper surface of this part, and a cast from 

 the original was taken to represent this portion in the restoration. 

 (2) The type of S. Lacoanus, Claypole, includes a large part of the 

 cephalothorax of an individual nearly the same in size as the 

 preceding. (3) Dr. J. M. Clarke discovered that this specimen also 

 preserved considerable evidence as to the nature of the appendages, 

 and he succeeded in developing what appear to be the chelate 

 antennje, the first pair of gnathopods, and the mandibular bases of 

 at least three others. (4) The length and number of joints in the 

 limbs are taken from the English species S. Logani and S. Powriei, 

 of which quite complete, though smaller, individuals have been 

 described by Woodward.^ (5) The outline and proportions of the 

 abdomen follow closely those of the English forms and of S. BeecJieri, 

 the latter giving the natural convexity. (6) A portion of a large 

 abdominal segment found by the writer in the Chemung group at 

 Warren, Pennsylvania, and apparently belonging to a nearly related 

 species, has an ornamentation closely approaching that on the 

 cephalothorax of the type, and was used to elaborate the sculpture 

 over the abdomen of the restoration. (7) The form and character 

 of the telson spine correspond to S. Logani and also to some large 

 fragments found by F. A. Eandall at Warren and Ackley, Penn- 

 sylvania, in the Chemung group, and probably belonging with the 

 abdominal somite already mentioned. 



With the data furnished by the foregoing material, the restoration 

 was undertaken. The first model in relief was constructed in clay, 

 and from it a plaster mould was taken. A number of casts have been 

 made since, and a photograph of one of them is represented in the 

 accompanying plate (Plate XVIII). 



In this connection, it may be suggested that the type-specimen of 

 Stylonurus (?) {MJiinocaris?) Wrightianiis (Dawson, sp.) represents 

 two proximal joints of one of the large crawling feet of a form 

 rekted to Stylonurus, and not two somites of the abdomen as 

 indicated by Hall.^ Any reference is at present somewhat uncertain, 

 owing to lack of positive knowledge, and the fact that the specimen 

 in question was first described as a plant {JEquisetides % then referred 

 to the Phyllocarida {EcMnocaris^), and lastly appeared as a possible 

 Merostome, shows how this form may be interpreted by different 

 observers. No one can doubt its arthropod nature, on account of 



^ Loc. cit. 

 ^ J. Hall : Note to explanation of plate xv of paper on Geology of Yates 

 County, N.Y., by B. H. Wright: Thirty-fifth Ann. Rep. N.Y. State Mus. Nat. 

 Hist., published 1884. " 



3 J. W. Dawson, "Notes on New Erian (Devonian) Plants": Quart. Journ. 

 treol. boc. London, vol. xxxvii (1881). 



* ti ■^"r?" ^^"^^^ ^ ^' "^oo'l^'ard, "Notes on Phyllopodiform Crustaceans, referable 

 to the Genus Echimcaris, from the PahTozoic Rocks " : Geol. Mag., n.s., Dec. Ill, 

 Vol. I, September, 1884. 



