484 J. J. S. Teall — Origin of Banded Gneisses. 



are to be relegated to the same division as the terrestrial traclieated 

 forms of the Arachnida, there is no need to offer any further evidence ; 

 but at present I deny, w^ith other Carcinologists, that Professor Eay 

 Lankester has proved his position, or that such an arrangement is 

 consistent with sound zoological classification. 



It is extremely interesting to record the fact that in 1881 Mr. J. 

 F. Mansfeld communicated an account, with a woodcut, of a fine 

 fossil Eurypterus found by him in the shale immediately beneath 

 the Darlington Cannel Coal-bed, Lower Productive Coal Measures, 

 Darlington, Pennsylvania, U.S.A. (See Amer. Phil. Soc. Proc. vol. 

 xix. p. 152, April 1st, 1881.) 



The figure I have seen, being only a sketch, and roughly executed 

 — without scale — does not admit of accurate comparison ; but so far 

 as I am able to judge, this American Eurypterus must have been 

 extremely closely related to our Eskdale species. 



As it is convenient to have a name for a new form, I propose to 

 designate this our second Scottish Eurypterus from the Carboniferous 

 series as E. scabrosus. 



Dimensions of Specimen. — Head 5f inches broad, by 4-| inches in 

 length. Lengtli of body (including head to seventh segment) 10 

 inches, perfect appendage 8 inches in length, widest part at third 

 segment of body 6|- inches broad. Total length estimated at about 

 20 inches, including the telson. 



EXPLANATION OF PLATE XIII. 

 Eurypterus scabrosus, sp. nov. 



Fig. 1. Larger slab containing the head with three of the gnathopodites in place 

 on the right side ; and the 1st to the 7th somites more or less perfectly preserved. 

 Fragments of the branchial leaves [br.) are seen on the left side of the head. 

 Prof. Huxley (who kindly looked at the original specimen) has suggested that 

 the portion of an appendage, with a row of small tubercles along its border 

 near the small figure 2, on the right side of the head, may possibly have been 

 a part of a chelate appendage ; but it is very obscure. Other fragments are 

 seen on the left side of the head (near 5) similarly ornamented. 



Fig. 2. A fragment of same specimen showing portions of the 8th to the 10th somites. 



II. — On the Origin of certain Banded Gneisses. 

 By J. J. H. Teall, M.A., F.G.S. 

 (PLATE XIV.) 



THE term gneiss as generally used by geological writers signifies 

 a rock of granitic composition in which a parallel structure in 

 the arrangement of the constituents is more or less apparent. For 

 our present purpose it is important to note that other plutonic rocks 

 besides granite {e.g. diorite, gabbro, and peridotite) have their 

 gneissose equivalents, so that, if we use the term gneiss in a structural 

 rather than in a mineralogical sense, we may speak of diorite-gneiss, 

 gabbro-gneiss, and so on.^ Now the parallel structure of gneissose 



^ Eoth has recently (Sitz. d. k. preuss. Akad. d. Wissen. Ueber den Zobtenit, vol. 

 xxxii. 1887, p. 611) proposed that Leopold von Buch's term Zobtenfels should be 

 revived under the form Zobtenite for those gabbros which are associated with crystal- 

 line schists and are often foliated. 



