Metamorphism of Massive Crystalline Rocks. 69 



Fig. Za k b. iYeHfo;jst« (?M«-m,HebertaiidDeslongchamps. Coral Rag probably 

 of Seamer or Ayton. Strickland Collection. Back and front. 



X H. 



,, 3c. Idem. Leckenby Collection. Natural size. 



,, 4« & 5. Turbo corallensis, Buvignier. Coral B,ag of Ayton. My 



Collection. Front and back, x 2. 

 „ bakb. Turbo Erinus, D'Orbigny. Coral Rag of North. Grimston. 



Strickland Collection. Back and front, x 2. 

 ,, 6. Tnrbo Icevis, BuYignier. Coral Rag of Hildenley. Strickland 



Collection. Back and front, x 2. 

 ,, 7a & b. Turbo (Delphinula) funiculatus, 'Phi\\i])S. Coral Rag of Brompton. 



Strickland Collection. Back and front, x l^. 

 ,, 8a & b. Turbo (Delphitm/a) Fellati, Be Loriol. Coral Rag of Langton Wold. 



My Collection. Fragment, back and front, x 1 J. 

 „ 9. Troc'hus obsoletuSj'RosTD.ei. Passage -beds of the Lower Limestones. 



My Collection, x 2. 

 „ 10. Trochus acuticarina, Buvignier. Corallian of Yorkshire. Leckenby 



Collection, x 2. 

 ,, lla & b. Trochus granularis, s^.n. Corallian of Yorkshire. Leckenby 



Collection. Back and base, x 2. 

 „ 12. Trochus Aytonensis, Blake and Hudleston. Base of Coralline 



Oolite, Pickering. Leckenby Collection, x 2. 

 „ 13. Trochus, sp. Coral Rag of Brompton. My Collection. Natural 



size. 



{To be continued in our next Number.") 



II. — On a Case in which various massive Crystalline Eocks 

 INCLUDING Soda-Granite, Quartz-Diorite, Noritb, Horn- 



BLENDITE, PyROXENITB, AND DIFFERENT ChRYSOLITIC RoCKS, 

 "WERE MADE THROUGH MeTAMORPHIC AgENCIES IN ONE MeTA- 



MORPHic Process. 



By Prof. James D. Dana, LL.D., A.M., For. Memb. Geol. Soc. Lond., 

 of Yale CoUege, New Haven, Ct., U.S.A.i 



THE hornblendic and associated rocks referred to in the above title 

 cover a large part of the township of Cortland — the north-western 

 of Westchester County, New York — between Croton Eiver on the south 

 and the parallel of Peekskill on the north, an area of about 25 square 

 miles. They differ widely from the ordinary rocks of the county, 

 and may well be designated the Cortland series. In fact, a series so 

 remarkable in constitution, so diversified in kinds, and so full of 

 geological interest, is seldom found together within so small an area 

 anywhere on the globe. They reach the banks of the Hudson just 

 south of the Peekskill railroad station, and at several points beyond ; 

 yet considerable portions of the shore region are occupied by narrow 

 strips of common kinds of mica schist and gneiss, and occasionally 

 limestone. Leaving Peekskill by South street, near the river, the 

 first ledges (&, on the following map) consist of one of the rocks of 

 the series; and to the eastward of the village, on the road leading 

 south-east, only half a mile from the Academy grounds (adjoining 



^ This article is one of a series by Prof. Dana on the Limestone belts and associated 

 rocks of Westchester County, New York, published in the American Journal of 

 Science, volume 20. Westchester County is the Southern County of Eastern New 

 York. The Hudson River bounds it on the west, and A^ew York Island — the site of 

 New York City— on the south. Its rocks are, with small exceptions, ordinary 

 gneisses, mica schists, and crystalline limestone. 



