566 Co7ifributions to Inverlebrale Palaeonfology. 



it slopes abruptly liat-kward to and along the basal line, and again more 

 abruptly curving around tlie posterior end of the valve and forward to the 

 extremity of the cardinal line; below which it is distinctly excavati-d. The 

 portion of the valve which projects beyond the hinge is nearly or (^uite equal 

 to one-third the length of the valve. Surface of the valves convex, and 

 marked by ridges and tubercles. The principal ridge commences at about 

 the anterior third of the valve, and just above the middle, as an elevated, 

 rounded, and nearly vertical ridge; but soon bends somewhat abruptly, and 

 is directed backward in a broad, sweeping curve, at less than one-third of 

 the height of the valve from the lower margin, and gradually decreasing in 

 strength terminates a little within the margin opposite the longest part of the 

 valve. A second ami slightly stronger ridge rises from just behind tlie middle 

 of the length of the hinge, and descends with a gentle forward curvature, 

 terminates near the upper anterior end of the first one. The anterior or prin- 

 cipal tubercle is large and distinct, and situated near the antero-dorsal angle 

 of the valve, occupying the greater part of the space between the front margin 

 and the two ridges just described. Between this and the second ridge the 

 surface is elevated, forming a low tubcnle. The surface of the anterior 

 tubercle is occupied by several small but distinct pustules, and the entire 

 surface of the valve covered by a minutely granulose structure. 



Abdomen apparently consisting of four free segments ; the first one being 

 short and much thicker than the others on the anterior end, but rapidly 

 narrowed posteriorly ; the posterior margin being armed with several small 

 spine-like tubercles. The other three segments are shorter than wide, gradu- 

 ally decreasing in sti-ength and increasing in length backwards, the first of 

 the three being apparently less than half as long as Avide, their posterior 

 margins all spine bearing ; a long curved lateral sj^ine on each side, with 

 three short ones between, and all increasing in length backwards from the 

 first or anterior segment. 



Telson iiroportionally large, of a general triangular form, but slightly pro- 

 truding at the origin of the movable spines, and projecting behind into a long, 

 slender, and apparently cylindrical spine, making the telson with its spine 

 about as long as the four free segments together. Lateral spines cylindrical, 

 very gently curved, and standing at an angle of about forty-Jive degrees to 

 the central spine. Surface of the telson highly convex and somewhat angular 

 at the origin of the spine. Surface of the crust of the abdomen smooth. 



This species is closely allied in the form of the carapace to E. 

 punctata Hall (16th Kep. State Cab. N. Y., p. 74, plate 8, i\g;. 1); 

 but dilTers in the form of the nodes and ridges, and in the surface 

 structure, also in wanting the projection at the ])osterior end of the 

 hinge; if this feature is natural on that specimen. It is probable 

 that the abdomen and telson figured on ilic same plate uiuU-r the 

 name Ceratiocaris armata, belong to the same species as the 

 carapace of E. punctata, as suggested by Frof. Hall in the expla- 

 nation of plate 28, section Crustacea, lUust. Dev. Fossils ; and if so, 



