Clarke — Oxkoxta. Ithaca a.m> Poetage Groups. 



69 



and more shaly, and contain Spirifer mucronatus var. posterns and Orthoceras 

 sp. Here also were found three specimens of an interesting species of 

 Mhmoccvris* 



Station VII. Buel's creek, one and one-quarter miles east of Truxton, 

 Cortland county. The exposure here consists at the base, of black, alternating 



* Rhinocaris (?) bipennis, sp. nov. This interesting species has a long and comparatively narrow carapace; in the hest pre- 

 served specimen the two valves appearing to be folded not exactly in the median line. The character of the hinge is obscured by 

 the manner of folding and it is not possible to determine whether the species possessed a median plate with a hinge on either side 

 as in true Rhinocaris, or whether the hinge line was actually median as in Elymocaris, Emmelezoe and Ceratiocaris, but the pre- 

 sumption from the general aspect of the carapace and from several other structural features, is that the fossil is a Rhinocaris. The 

 anterior outline presents a somewhat truncate extremity which may have been prolonged into an acute termination as in many 

 such carapaces, but as the specimen is somewhat broken at this point, its character can not be made out. There is no evidence 

 of a movable rostrum. The lateral margins make a broad and low curve of about equal degree before and behind, and posteriorly 

 the margin seems to have been somewhat truncated or slightly incurved, the specimen being somewhat imperfect here. The 

 lateral surface of each valve bears a single fine sharp ridge, scarcely developed into such a carina as characterizes the single keeled 

 genera Echinocaris and Ptychocaris. This ridge makes an ogee curve, bending downward in front and upward behind, becoming 

 obsolete on the posterior region of the carapace. A very distinct ocular node lies at about one-third of the length of the carapace 

 from the anterior extremity; at its summit the surface is smooth and bears a well-defined circular optic pit, as in Rhinocaris and 

 Mesothyra. The ornamentation of the carapace is quite peculiar ; the region above the ogee ridge is marked by elevated, chevron- 

 shaped or squamose lines which are sharpest at the anterior extremity, becoming more diffuse and less obscure posteriorly. Their 

 general direction is parallel to the hinge, though they curve around the optic and mandibular nodes. Below this curved ridge the 

 surface is quite smooth except near the margins where there are a few faint anastomosing lines such as most of the Phyllocarida 

 possess. The outer margins of the valves are thickened and the surface slightly grooved within them. Besides the optic node 

 there is a well-defined node just behind it, probably of muscular or mandibular origin and some other ill-defined node-like irreg- 

 ularities on the surface which are probably due largely to compression. The abdomen is partially obscured at its proximal end, 

 but shows three segments, the first two comparatively short, the third long, cylindrical and marked with oblique lines. These 

 segments arc similar iu relative size and aspect to those of the Hamilton species, R. columbina, and are a further reason for 

 assigning this species to the same genus with that. The telson is produced into a spine which appears to have been somewhat 

 shorter than the cercopods, though it is not complete. One of the cercopods is preserved, a long slender spir.e, striated as in 

 Mesothyra and bearing a crenulated inner margin which was the base of insertion of a setal fimbriae. This is also a feature well 

 defined in the specimens of the great Mesothyra Oceani, from the Ithaca fauna at Ithaca. 



The accompanying sketch shows the described specimen in its natural proportions. 



Traces of appendages. One of the specimens has lost the carapace by exposure to weather and shows traces of certain 

 struciures of the inferior surface. Exceedingly little is known of such structures in the fossil Phyllocarida. In an obscure 

 species from the Carboniferous concretions of Mazon creek, Illinois, termed by Packard Cryptozce, Beecher made out traces of 

 two or three cephalic appendages, which have been described and illustrated by the former writer; and Whitfield has figured 

 examples of Enlomocaris and Ceratiocaris, showing evidence of thoracic legs. What is here visible in Rhinocaris is not re::dily 

 resolvable into agreement with the structure of the living Nebalia, but is described simply as it appears without any attempt to 

 homologize the parts. 



In this specimen the removal of the carapace has left exposed a portion of the under side covering rather more than the area 

 ofone valve. The most prominent features of the exposed surface are two angular hcmi-lozeuge-shaped plates, whose edge is 

 sharply lined like marginal portions of the carapace (marked Pin the figure) These lie in a somewhat symmetrical position with 

 reference to each other, but that at the left is more fully retained than the other. The striated, sharply angled margin appears at 

 first glance to be a lamellate body by itself, but closer inspection shows it to be continuous with a smooth area or plate whose out- 

 line is not very distinctly retained. Behind these lies another smooth somewhat quadrangular area, the margins of which are 

 thickened, striated and continue \ backward. The bodies P P may possibly have teen united into one trapezoidal plate, although 

 the inner margin of P seems to be partially entire. In front of these plates aie five flat and narrow impressions separated by their 

 ridges. All are so directed as to converge to the same area. The fifth or last of these impressions seems to have a somewhat 

 definite outline and to be faintly striated. The general aspect of these markings and their position suggests that they are rem- 

 it :nts of cephalic appendages, the narrow ridges being the filling of the spaces between them. 



