PLATE XXXI— Continue.! 

 Fiff. 1 1. The right valve of a small individual, slightly broken at the anterior extremity, lmt showing the 

 sharply angular posterior extremity of the hinge. This valve is somewhat broader posteriorly 

 than that represented in tig- 7, and as it appears to be uncompressed this outline is probably 

 correct for the species. 



Chemung group. Warren, Warren county, Pennsylvania. 

 Pig. 12. Two of the abdomen and a portion of the telson, referred with doubt to this species. 



The drawing is enlarged to two diameters to show the character of the surface markings. 

 Chemung group. Warren, Warren county, Pennsylvania. 



Tropidocaris interkupta. 



Page 185. 

 Fig. 13. A right valve of the carapace, showing the form and surface ornamentation. 

 Chemung group. Warren, Wan-en county, Pennsylvania. 



Tropidocaris alternata. 



Page 186. 

 Fig. 14. An imperfect left valve, showing the numerous carinas and the nodes in the cephalic region. 



Waverly group. Warren, Warren county, Pennsylvania. 

 Fig. 15. Another imperfect left valve, showing the carinas and bearing the impression of plates of an 

 echinoderm. 

 Both this and the preceding figure have been drawn from gutta-percha impressions taken from 

 natural moulds of the dorsal surface. 



Waverly group. Warren, Warren county, Pennsylvania. 



Rhinocaris columbixa. 



Page 19S. 

 Fig. U'>. A carapace which has been laterally compressed, but retains the prora. Near the dorsal margin 

 is seen the line along which the carapace has been fractured. The surface shows no ornamen- 

 tation except the faint striae along the margins. 

 Fig. 17. The anterior portion of the same specimen, enlarged to two diameters to show the character of the 

 prora. The carapace has been fractured near the base of the prora, but upon the dorsal sur- 

 face the latter is continuous with the shield. 



Hamilton group. Tickenor's Glen, Canandaigua Lake. 

 Fig. 18. A portion of the carapace upon which lies a very small mandible. 

 The specimen is enlarged to three diameters. 



Hamilton group. Vinegar Brook Glen, Cayuga Lake. 

 Fig. IS*. A fragmentary specimen, showing a portion of the carapace, three segments of the abdomen, the 

 sub-conical caudal plate and telson, with the cercopods. 



Hamilton group. Vinegar Brook Glen, Cayuga Lake. 

 Kig. 20. The posterior portion of a large carapace, showing the character of the posterior margin. 



Hamilton group. Tichenor's Glen, Canandaigua Lake. 

 Fig. 21. An imperfect specimen retaining one side of the carapace, showing the last abdominal segment 

 and the telson. 



Hamilton group. Eighteen-mile Creek, Erie county. 



Rhinocaris scaphoptera. 



Page 197. 

 Fig. 22. A view of the left side of a carapace which has been crushed along a line lying to the left of the 

 axis, making this side appear narrower than is normal ; showing the prora, the conspicuous 

 lateral carina and the surface ornamentation. 

 ! 23. The anterior portion of the same specimen, enlarged to two diameters to shew the character of the 



prora, which is continuous with the carapace. 



Hamilton group. Tichenor's Glen, Canandaigua Lake. 



