196 
Theose 11 in 10 min., submucronate, slightly curved, inclined to the 
axis of the stipe at an angle of between 35® and 40°, three times as long 
as wide, in contact for two-thirds of their length. Apertural margin, 
slightly concave, almost' normal to the axis of the thecae (forming an 
angle of 115° with the axis of the stipe). Main stipes (second order) 
have an observed length of 25 mm., but probably are much longer, 
are straight and .rigid and of uniform width from about 4 mm. from tlie 
bifurcation to their distal extremities. Lying at right angles on oppo¬ 
site sides of the stipes of the first order (‘‘ funicle ”) each pair of 
opposite stipes are in the same straight line, imparting to the polypary 
its characteristic H symmetry. 
Remarks. —Nicholson’s original description^ was as follows: — 
Frond consisting of four simple undivided stipes, arranged bilaterally, 
two proceeding from each extermity of the funicle. Regarding the 
funicle as horizontal, the stipes are as nearly as possible at right angles 
to it; so that the two stipes on either side of the funicle form nearly a 
straight line. Stipes curved at their origin from the funicle, and then 
running nearly straight and parallel to one another. The entire form 
closely resembles two examples of Didymograpsus (Graptolithus) 
paiulus, Hall, united back to back by their radicles. Dimensions of the 
frond in the largest specimen observed:—Length of funicle, one-tenth of 
an inch; width of funicle, one-twentieth of an inch; total length of 
frond unknown, but exceeding 3^ inches; distances between the stipes 
opposite sides of the frond from one-fifth to one-fourth of an inch, 
except close to the funicle. Cellules about twenty-five in the space of 
1 inch, inclined to the axis at about 45°; the denticles prominent and 
slightly pointed or submucronate; the cell-mouths curved at right angles, 
or nearly so, to the cellules, and making an angle of about 135° with 
the axis.” 
The following is a comparative tabulation of the specific characters 
of the type species and that from Victoria :—- 
1 
Nicholson. 
Victorian Species. 
Thecae in 10 mm. 
10-11 
11 
Angle of inclination— 
,, distal thecae 
45° 
38° 
,, proximal thecae (approximate) 
20°-30° 
20° 
Overlap 
i_a 
2 3 
A--S 
^ 3 
Apertural margin 
submucronate 
submucronate 
slightly concave 
slightly concave 
Angle (average) of apertural margin to 
axis of stipe 
112° 
103° 
Maximum observed length of stipe • 
88 mm. 
25 mm. 
Width of main stipes distally ... 
aibout 2 mm. 
2 mm. 
Width of main stipe proximally 
about '6 
•6 
Ventral margin 
slightly concave 
concave 
Length of stipe of first order (funicle) 
2-6 
2*3 
Width of stipe of first order 
1-3 
1-1 
Affinities. — T. approximatus is more nearly related to T. acclinuns 
sp. nov. (p. 198 post) than to any other species yet described from 
Victoria or elsewhere; the essential differences are treated on when con- 
> Ann. and Mag. of Nat. His. 4th Ser. Vol. XI. (1873), p. 136. 
