422 NEW YORK STATE MUSEUM 



dated species have received but comparatively little attention. 

 The study of these has indicated the probability that we may 

 not be altogether secure in the time-honored interpretation and 

 correlation of some of our other strata having similar lithologic 

 characters, such for example as the Coralline limestone of 

 Schoharie county and the waterlimes of eastward sections. 

 The fauna of a specially interesting outcrop of dark dolomite 

 appearing on Frontenac island in Cayuga lake, where it is inter- 

 calated between the waterlime strata, will, when fully studied, 

 give important aid in the interpretation of the proper relation 

 of these beds to those which they immediately precede in time 

 and to which they are otherwise allied, that is to the true Helder- 

 bergian strata. Collections were made at and about Jerusalem 

 hill, and these operations were not concluded at the time of my 

 last report. It may be briefly stated that the sum total of the 

 latter work, which was devoted specially to the acquisition of 

 the crustacean remains at this locality, has afforded us much 

 interesting and unique material, not only increasing our knowl- 

 edge of these unusual and peculiar creatures, but also yielding 

 important evidence as to their early stages, their mode of 

 development and habits of life. I note here the fact that from 

 these collections we have obtained not only the most minute of 

 these creatures yet recorded, but also the remains of the largest; 

 heads of Eurypterus not -Vmch across, indicating young forms 

 not above J inch in entire length and fragments of a single in- 

 dividual of the genus Pterygotus which could not have been less 

 than 5 to 6 feet in length and thus representing one of the 

 largest known of all invertebrate fossils, surpassing probably 

 in size the similar crustacean, Stylonurus excelsior, 

 whose parts have been found in the Catskill or late Devonic 

 rocks of this state. 



Paleontologic and stratigraphic map of Canandaigua lake region. 

 In pursuance of a widely expressed desire on the part of many 

 American geologists that the effort be made to portray on maps 

 with more exactitude and fulness the paleontologic facts or 

 actual succession of vital events in the earth's history, I have 



