664 J. HOPKINSON AND C, LAPWOETH ON THE GEAPTOLITE8 OF 



served differently from any other species in these rocks, being simply 

 impressions on the surface of the shale. 



Fig. 5 a is from an original specimen collected by Mr. Hicks in 

 1865. 



Log. Lower Arenig, Road Uchaf, Eamsey Island, and Whitesand 

 Bay. Middle Arenig, Whitesand Bay (Camb, Mus.). 



Dendeogeapttjs diveegens, Hall. PL XXXYI. figs. 6a & 6b. 



1865. Dendrograptus divergens, Hall, Grapt. Quebec Group, p. 129, 

 pi. xvii. figs. 3, 4. 

 Narrowly cup-shaped in form, usually of minute size ; branches 

 slender, bifurcating at frequent regular intervals, diverging 

 very widely from each other at first, but soon curving inwards 

 so as to become almost, and frequently quite, parallel ; consider- 

 ably thickened at their points of bifurcation. 

 A few specimens, showing the above characters only, have been 

 found. In their general aspect, and in the regularity of the bifur- 

 cation of the branches, these specimens agree with Hall's figures ; 

 but the angle of divergence of the branches is not quite so great as 

 in the example figured by him from the Quebec Group, and the 

 thecse cannot be made out. Hall, however, says that in his speci- 

 men the thecae " are only determined by indentations in the shale." 

 Log. Lower Arenig, Boad Uchaf, Ramsey Island. 



Dendeogeapttts (?) difeusus, Hall. PI. XXXYI. figs. 7a & 7 b. 



1865. Dendrograptus ? (Callograptus?) diffusus, Hall, Grapt. Quebec 

 Group, p. 132, pi. xviii. figs. 1-3. 

 Diffuse and irregular in form ; branches strong, bifurcating fre- 

 quently and irregularly, and bending slightly at each bifurca- 

 tion ; surface irregularly corrugated and marked with minute 

 indentations, about 36 to the inch, which indicate the apertures 

 of the hydrothecee. 

 This species, in its mode of branching, and in its general aspect, 

 is a true Dendrograptus ; but its thecse are quite unlike those of the 

 typical forms of this genus, being indicated only by minute indenta- 

 tions, as in the genus Galhgraptus. In the specimen figured, how- 

 ever, where these indentations are not seen, the corrugations appear 

 occasionally to be discontinuous or transversely jointed, thus some- 

 what resembling the thecaa of Dendrograptus, which they probably 

 represent. These appearances, however, are not sufficiently defined 

 to be represented in the figures. 



Log. Lower Arenig, Boad Uchaf, Bamsey Island. 



Denpeogeaptus Bamsati, Hopk.j sp. nov. PI. XXXYI. 

 figs. 2a & 2b. 



Diffuse and irregular in' form, branching at irregular usually some- 

 what distant intervals ; branches flexuous, very gradually de- 

 creasing in width from about one twelfth of an inch near 

 their origin to one hundredth at their extremities, irregularly 



