1862.] HARKNESS SKIDDAW SLATE SERIES. 139 



Prof. M'Coy and Mr. Selwyn to the International Exhibition, a 

 large series of Graptolites appeared ; and these agreed, genus for 

 genus, and almost specifically, with our North-of-England forms. I 

 cannot think this accidental, and believe, therefore, that there is a 

 peculiar zone or horizon of the Llandeilo rocks of which these genera 

 of Graptolites are characteristic*. 



The mass of the Llandeilo strata is not tenanted by such compound 

 forms. The species of Didymograpsus known in the Upper Llandeilo 

 have the branches diverging at a moderate angle, while the strata 

 known as Lower Llandeilo in England have the widely diverging 

 forms of this genus, and such are found in the Skiddaw slates. 



In Canada the age of the Quebec series is still under discussion ; 

 but all agree in placing it low down in the Silurian series f. Here the 

 association of these Graptolites with Trilobites is such that we must 

 either refer them to the Primordial group itself, which is unlikely, or 

 allow that they represent the lowest beds of Lower Silurian rocks, 

 the passage-beds from the Primordial zone to the Llandeilo flags, — 

 the age, in fact, of the Tremadoc slates and Lower Llandeilo. 



With regard to the so-called sea-weeds, fucoids, &c, I have shown 

 elsewhere reason for believing that nine-tenths of these are due to 

 the action of marine worms. In the Skiddaw slate series there are 

 found abundant traces of these markings. 



Caryocaris, gen. nov. C. Wrightii, sp. nov. Eig. 15. 



A long, pod-shaped, bivalved carapace (with distinct hinge-pits), 

 rounded anteriorly, subtruncate behind, and with the back and front 

 subparallel. The surface is smooth, or with only oblique wrinkles 

 near the margins, but with no parallel lines of sculpture. Body ? 

 Telson and appendages ? 



All I know of this pretty little Crustacean, an inch long, and 

 rather more than one-third of an inch wide, is contained in the above 

 note. I was fortunate enough to find the tubercles (Huxley found 

 them also in Ceratiocaris), which I suppose indicate teeth (and cor- 

 responding pits) at each end of a short hinge -fulcrum. They are 

 marked a. 



The shelly carapace is solid for its size : it appears to have a good 

 deal of lime in its composition. The genus is evidently distinct, 

 though so little is known of the entire form. 



Loc. Everywhere in the Skiddaw Slate district. I have named it 

 after Mr. Bryce M. Wright, of Great Russell Street. 



Dichograpstts, gen. nov. Eigs. 9 to 12. 



Frond repeatedly dichotomous from a short basal stipes into 8, 16, 



* There is even a Crustacean, apparently of the genus Caryocaris, which 

 M'Coy has done me the favour to name Hymenocaris Salteri. 



f Hall has definitely added (see Proc. Amer. Phil. Soc. 1862) his opinion to 

 give weight to the idea that the Quebec Graptolite-group (including the Hudson 

 slates west of the river, as decided by Logan's discovery of the great fault) implies 

 simply a different condition of the Calciferous Sandstone. " Quebec group " 

 would surely be a better term; or why not "Skiddaw group"? It is the 

 oldest. 



