October, 1913. New Trilobites — Slocom 83 



plcte pygidium. In general form this species resembles P. callicephalus 

 but differs from it in the following characters: In P. larrabeei the 

 cephalon is longer in proportion to the width; the cheeks do not curve so 

 abruptly to the lateral margins; the glabella is less inflated anteriorly; 

 the pygidium is longer and has more annulations and segments; the 

 pustulose surface occurs only on the glabella; the surfaces of the pal- 

 pebral lobes, occipital ring and checks are punctate. The pygidium of 

 P. larrabeei appears to be midway between P. callicephalus and P. 

 intermedins in form. The specific name is given in memory of the late 

 Ex-Governor William Larrabee on whose property some of the speci- 

 mens were collected. 



Locality and horizon.- — More or less complete cephalons and 

 pygidia are comparatively abundant in the Lower Maquoketa beds at 

 Clermont, Elgin, and Bloomfield. The type specimen came from 

 Clermont. 



ACKNOWLEDGMENTS 



The generic descriptions used in this paper have been derived from a 

 number of sources. Where practicable a copy of the original description 

 of the genus has been given ; in other cases the best descriptions available 

 have been used. In nearly all cases the descriptions have been rewrit- 

 ten, but where copied due credit has been given. 



The writer is under obligations to Mr. A. G. Becker of Clermont for 

 the loan of specimens and assistance given while in the field. Mr. 

 Becker not only placed his private collection at the disposal of the 

 writer, but spent much time with him in actual collecting and gave 

 valuable information as to localities to be visited. Also to Prof. 

 George F. Kay for the loan of specimens from the paleontological col- 

 lections of the State University of Iowa, and to Prof. Stuart Weller of 

 the University of Chicago for the loan of type specimens and publica- 

 tions which materially aided in the preparation of this paper, grateful 

 acknowledgments are given. 



