GD R. R. GURLEV 
line) again on the over side, and the same phenomenon is repeated with each 
loop. Thus the theca are always on the ow/ey margin on the /ower, and on 
the zzer margin on the wpper half of each loop. Further between the two 
branches at their points of crossing a film of shale can frequently be seen, the 
branches lying in the shale at slightly different levels. Also the branches always 
cross alternately over and under. All this is easily and only explicable upon 
the supposition that the branches originally grew sfzva//y upward, each describ- 
ing an oppositely directed curve. Compression would then produce the suc- 
cessive ellipses with the thece directed alternately outward and inward. This 
mode of growth in a continual spiral seems, as far as I can judge from Lap- 
worth’s figures of the species, to be exhibited by his Décellograpsus caduceus 
and D. ztczac. 
Relative to its generic affinities it has been referred to both Dicellograpsus 
and to Dicranograptus, Waving early noted the presence of the thecz on 
the concavity of the first curve and the specimens not being the best, I thought 
it possibly a Dicellograpsus of the caduceus type, in which the first loop was 
closed. Better specimens, however, seem to show conclusively that the 
branches are united as in Dicranograptus. This portion is very short and like 
several other species it presents in this respect an approximation to Dzced/o- 
grapsus. 
Horizon and locality.—Lower Dicellograpsus zone (of which it is one of 
the most characteristic species) near Stockport, Columbia county, N. Y. 
Dicranograptus nicholsont Hopkinson. 
GEO, Mire, WIM WSO} [Os B57 Plate OWI, Wise 3 
This species occurs in the Utica under a form which Professor Lapworth 
informs me does not differ from the typical. 
Dicranograptus nicholsont arkansasensis Gurley, 1892. 
Dicranograptus arkansasensis, Ann. Rep. Geol. Surv. Ark., for 1890, III., 
Doo HUO—7/, IFES IDK. IPI Uy Bs 
Proximal portion 9™™ long ; branches diverging at an angle of go° to 130°, 
curving upward at a short distance from their origin so as to include a smaller 
angle; thecze 20 in the space of 25™"; non-spinose. 
Horizon and locality.— Lower Dicellograpsus zone, Arkansas. 
Dicranograptus nicholsont whitianus (Miller), 1883. 
Graptolithus (Climacograptus) ramulus White (preoc.), 1874, Prelim. 
Rep. Invt. Fossils, p. 13; 26., White, 1875, Rep. Wheeler Survey, 
IV., Part I., p. 62, Plate IV., Figs. 3a-e; Graptolithus whitianus 
Miller, 1883, Cat. Amer. Pal. Foss., 2d ed., p. 269; Decranograptus 
ramulus Herrman, 1886, Nyt Mag. f. Naturvidensk., XXIX. 
This form differs from the typical D. zzcholsonz of the Utica in the smaller 
