TALEONTOLOGIC CONTRIBUTIONS IO7 



but slightly outward curving line passing backward from the 

 frontal margin. One of our specimens shows a faint black suture 

 line passing in the direction indicated in figure 7, plate 33. 



The best preserved of the carapaces of P. roosevelti show 

 the anterior projecting point to be strengthened by a trapezoidal 

 prominence (see pi. 33, fig. 6). 



An accomplishment, well known among trilobites and other 

 crustaceans but hitherto not observed among Synxiphosurae and 

 other limuloid arachnids, is the power of enrolment. Yet one 

 specimen (pi. 33, fig. 6) has the abdomen distinctly rolled partly 

 under the carapace and the pleura sliding under each other 

 in forward direction in such a way that an accidental post-mortem 

 rolling up seems excluded, especially since the carapace is the best 

 preserved in the collection. Doctor Clarke has already pointed out 

 the many trilobitelike features in this arachnid ; the power of 

 enrolment would be another peculiarity, apparently connecting the 

 two. From evidence on the phylogeny of the Merostomata set 

 forth in the monograph of the Eurypterida of New York, it seems 

 probable that these similarities are due to a convergence resulting 

 from similar habits and not to actual relationship. 



Pseudoniscus clarkei nov. 



Plate S3, figures S and g 



In the report of the State Paleontologist for 1900 (p. 89), Doctor 

 Clarke has described as P. roosevelti the first representative 

 of this rare and interesting genus of Synxiphosurae before only 

 known from the Silurian of Oesel, Russia. Doctor Clarke had 

 then only the specimens from the Pitts ford shale in the collection 

 acquired from Mr Clifton J. Sarle, and one specimen from the 

 Bertie waterlime at Litchfield. Since that time considerable more 

 material has been obtained, partly collected by Mr H. C. Wardell 

 and the writer in the canal bank at Pitts ford, and partly in the 

 Bertie waterlime by Mr C. A. Hartnagel. These specimens not 

 only exhibit a number of new features of P. roosevelti, but 

 also indicate that the specimens from the Bertie waterlime belong 

 to a different species. Since in the whole P. roosevelti is 

 better preserved than the new species, P . clarkei, and the 

 former has been elaborately described by Doctor Clarke, we deem 

 i.t sufficient to note the differences between the two species. 

 " The carapace of P . clarkei is relatively longer and narrower 

 than that of P. roosevelti (in the former the length is to the 



