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



discovered that this specimen also preserved considerable evi- 

 dence as to the nature of the appendages, and he succeeded in 

 developing what appear to be the chelate antennas, 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. Rowriei, of 

 which quite complete, though smaller, individuals have been 

 described by Woodward. 10 (5) The outline and proportions 

 of the abdomen follow closely those of the English forms and 

 of S. Beecheri, 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 appar- 

 ently belonging to a nearly related species, has an ornamenta- 

 tion 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 frag- 

 ments found by F. A. Randall at Warren and Ackley, Penn- 

 sylvania, in the Chemung group, and probably belonging with 

 the abdominal somite already mentioned. 



With the date furnished by the foregoing material, the 

 restoration was undertaken. The first model in relief was 

 constructed in clay, and from it a plaster mold was taken. A 

 number of casts have been made since, and a photograph of 

 one of them is represented in the accompanying plate (Plate I). 



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

 men of Stylonurus (?) {EchinocarisX) Wrightianus (Dawson 

 sp.) represents two proximal joints of one of the large crawl- 

 ing feet of a form related to Stylonurus, and not two somites 

 of the abdomen as indicated by Hall. 5 Any reference is at 

 present somewhat uncertain, owing to lack of positive knowl- 

 edge, and the fact that the specimen in question was first 

 described as a plant (Equisetides 2 ), then referred to the Phyllo- 

 carida (Echinoca?"is 8 ), and lastly appeared as a possible Meros- 

 tome, shows how this form may be interpreted by different 

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

 of the characteristic surface markings. Its elliptical or ovoid 

 section without any flattening of the epimera, the very consid- 

 erable overlapping of the joints, and the configuration of the 

 suture, are more strongly indicative of the nature and require- 

 ments of a limb than of abdominal segments. 



The Relief Model. 



In this restoration, the animal is represented as lying on a 

 slab, with the entire dorsal surface exposed. The cephalo- 

 thorax has an axial length of 25 cm and a width of 22 cm . 



