56 



BULLETIN 65, UNITED STATES NATIONAL MUSEUM. 



generic form resembles Dcndrograpsus, but it is stronger iind more bushy than 

 species of that genus, and has conspicuous spines indicating a different cell 

 structure [in whoso axils the thecte were probably situated; 1884]. 



Gurley adds in his manuscript to Spencer's definition of the genus: 



This is apparently a good genus, including several species which present a 

 very similar facies, principally in the plumulose branches with a tendency to 

 a 2- or 3-spicate termination. But if this genus be altogether distinct from 

 Inocaulis (a point on which at present I do not feel positive), it is certainly 

 here that Spencer's Inocaulis walkeri belongs. 



Genotype. — Acanthograptus grantl Spencer. Niagaran (Ix)ck- 

 port), Hamilton, Ontario. 



ACANTHOGRAPTUS GRANTI Spencer. 



Plate 2, figure 1 ; Plate 3, figure 4. 



Acanthof/rnp'^uft grariti Spencer, Canadian Nat., VIII, 1878. pp. 458, 4G1. 462. 

 Acanthograpius granti Spencer. Canadian Nat., X, 1882, p. 165 ; Trans. 



Acad. Sci. St. Louis, IV, 1884. pp. 564, 582, pi. 4, fig. 5; Bull. Mus. 



Univ. State Missouri, I, 1884, pp. 14, 32, pi. 4. fig. 5. — Gurley, Journ. 



Gool.. IV. 1806. pp. 92, 308. 



The original description is as fol- 

 lows: 



Frond shrublike, with thick branches lU'in- 

 cipally originating near the base. Some of 

 the branches are bifurcated and have the 

 ends dichotomous ; cell apertures on one side 

 only, and indicated by pi-ominent spines 

 which appear to be placed below them. The 

 l)ranches are sometimes the sixteenth of an 

 inch broad, with spines in some places pro- 

 .iecting the twenty-fourth of an inch and 

 ending abruptly. 



The larger fronds do not exceed two 

 inches in height and sometimes have the 

 same width. 

 This species was first obtained [in the Niagaran dolomites: 1884] at Hamilton, 

 Ontario, by Colonel Grant. 



The description of 1884 adds the following data : 



Surface longitudinally striated. Occasionally there are rudimentary denticles 

 appearing also on the opposite side of the branch as well as on that marked 

 with the regular spinelike pro.iections, of which thei'e are 6 or 7 in the length 

 of a centimeter of the stipe, which is characterized by obscure indications of a 

 solid central axis. The branches average a millimeter in breadth, and the 

 spines are sometimes a millimeter long, which in some places extend into the 

 material of the stipe to its center. The flattened frond is usually 4 or 5 cm. 

 high and about 4 wide, and consist of 15 or 20 branches at half its height, 

 which are somewhat more numerous at the sunnnit, owing to occasional 

 bifurcations. The whole frond originates from a common radicle. 



Pig. 72. — Acanthograpius granti 

 Spencer. Copy of Spencer's 



FIGURE. 



