650 J, HOPKINSON AND C. LAPWOETH ON THE GEAPTOLITES OF 



1865. Graptolithus quadribrachiatus, Hal], Grapt. Quebec Group, 



p. 91, pi. v. figs. 1-5, pi. vi. figs. 5, 6. 

 1874. Tetragraptus quadribrachiatus, Ether, jun. Ann. <fc Mag. Nat. 

 Hist. ser. 4, vol. xiv. p. 3, pi. iii. figs. 5-8. 

 Branches straight or nearly so [springing bilaterally and symmetri- 

 cally from either side of a short slender funicle], gradually in- 

 creasing in width from about one twentieth of an inch at their 

 origin to one tenth at their extremities ; virgula very distinct ; 

 periderm well marked, narrow ; hydrothecae from 20 to 24 to 

 the inch, inclined to the axis at an angle of 30° or 40°, about 

 four times as long as broad, and free for one third to one 

 half their length, transversely striated, and slightly expanding 

 towards their extremities ; apertural angle 95° to 100°, margin 

 nearly straight. 



Associated with the other species of this genus here described 

 there occur single branches having all the characters of this species, 

 and agreeing precisely with Hall's description. In one or two spe- 

 cimens the branches are broken off, so as just to show a small portion 

 of the funicle, but barely sufficient to determine the form to be 

 a Tetragraptus. The characters shown by the isolated branches, 

 however, are sufficiently distinctive. 



Loc. Middle Arenig, Whitesand Bay. 



Teteaoeapttjs sebea, Brongniart, sp. PL XXXIII. fig. 10. 



1828. Fucoides serra, Brongn. Hist. Yeg. Foss. vol. i. p. 71, pi. vi. 

 figs. 7, 8. 



1851. Graptolithus Murchisoni, Bceck (in part), Bemarkn. Grapt. 



p. 10, pi. ii. fig. 30. 



1852. (?) Claclograpsus serra, Geinitz, Die Graptolithen, p. 30, taf. v. 



figs. 32-35. 

 1858. Graptolithus bryonoides, Hall, Eep. Geol. Surv. Canada for 



1857, p. 126. 

 1863. Tetragrapsus bryonoides, Salter, Quart. Journ. Geol. Soc. vol. 



xix. p. 137, fig. 8 a. 

 1865. Graptolithus bryonoides, Hall, Grapt. Quebec Group, p. 48, 



pi. iv. figs. 1-11. 

 1868. Didymograpsus bryonoides, Carr. Geol. Mag. vol. v. p. 129. 

 1874. (?) Tetragraptus bryonoides, Ether, jun. Ann. & Mag. Nat. 

 Hist. ser. 4, vol. xiv. p. 2, pi. iii. figs. 1-4. 

 Branches connected by a short funicle, in the centre of which the 

 sicula is usually seen as a minute triangular process, diverging 

 at various angles, narrow at their origin, but soon acquiring 

 their full width of from one tenth to one eighth of an inch, 

 which they maintain to near their distal extremity, which is 

 abruptly rounded and occupied by the partially developed hy- 

 drothecse ; hydrothecse from 20 to 24 to the inch, inclined to 

 the axis at an angle of 40° or 50°, four times as long as wide, 

 free for about one fourth their length, and slightly recurved 



