106 NEW YORK STATE MUSEUM 



Fr. Schmidt in his Crustaceenfauna der Eurypterenschichten in 

 Rootsikiill auf Oesel, 1 has redescribed the only Pseudoniscus then 

 known and states that he can not see eyes in the incisions observed 

 by Nieszkowski and moreover has found the suture line in a speci- 

 men without any opening for the eyes. He adds, however, that he 

 noticed on 'the right cheek a slight elevation that might be adduced 

 as indicating an eye. 



P. roosevelti was the second species described of Pseudo- 

 niscus. Doctor Clarke made a careful search for eyes. He states 

 (Rep't N. Y. State Pal. for 1900, p. 89) : "In all the specimens 

 studied there is no evidence that can be construed as indicating the 

 position or presence of eyes. The more complete specimens show 

 certain wrinkles or ridges concentric to the margin, whose very 

 obscurity might be regarded as veiling the eyes which from analogy 

 one would expect to find in this creature ; other shields show 

 irregular swellings which are, in part at least, due to underlying 

 carapaces of Leperditia, but the most favorably preserved demon- 

 strate that it would be an error to let any such irregularities pass 

 as an apology for eyes." It is obviously on account of these ob- 

 servations that Pseudoniscus in the new edition of Zittel-Eastman, 

 page yyy, is stated to be probably eyeless, while in the preceding 

 edition it was considered as having large compound eyes. 



The question of the eyes of P. roosevelti has been solved 

 by four specimens since brought in from Pittsf ord ; two of these 

 show the eyes distinctly on the inside of the carapace and two 

 others on the outside ; one specimen also exhibits the facial sutures 

 passing around the eye. These eyes are, however, in contrast with 

 the supposition of Nieszkowski and Woodward, very small and 

 situated much forward and near the margin (see pi. 33, fig. 6). 

 Since they are small and of lunular outline and situated on 

 the brow of the elevation of the carapace, any flattening or dis- 

 tortion of the carapace is very apt to close or compress them into 

 an insignificant line, a mode of preservation of the eyes often also 

 observed in Otisville shale material of eurypterids. A reinspection 

 of the original material of P. roosevelti proves that that is 

 precisely what has happened there. The specimens of P . c 1 a r k e i 

 show the eyes as minute lunular puckers at an exactly correspond- 

 ing place. 



The suture line was already observed by Schmidt on one cheek of 

 P. aculeatus {op. cit., pi. 1, fig. 49) as a nearly straight or 



1 Miscellanea Silurica III, Mem. de l'Acad'. Imp. des Sciences de St- 

 Petersb., 7 ser., t. 31, no. 5, p. 40. 1883. , 



