NORTH AMERICAN GRAPTOLITES 75 
both proximally and distally for about 25" without very obvious decrease in 
size. Theca 16 to 20 in 25™™", appearing to form bent tubes. 
Horizon and locality—Upper Dicellograpsus zone, Magog, Canada. 
Climacograptus caudatus laticaulis Gurley, var. nov. 
(Climacograptus caudatus Lapworth, 1877, Ann. Rep. and Proc. Belfast 
Nat. HieldiGlub; > Part lV, p. 136, Plate Vil, Fig. 34°) 
Polypary reaching a length of 60™" or somewhat more; usually shorter ; 
maximum width attained at extreme proximal (‘distal’) extremity, usu- 
ally 3.5"™" or a little more. Outline of polypary obtriangular, continuously 
widening from the rather blunt, 1™" wide distal (‘‘ proximal’’) extremity to 
the abruptly truncated proximal (‘‘distal’”’) extremity. Distal (‘‘ proximal ’’) 
extremity marked by two rather small lateral spines and further by the pro- 
longed virgula. Virgula strap-like, prolonged both proximally and distally 
at least 25" without any evidence of termination. In the distal (‘‘ proximal”) 
direction, the diminution in size in the distance mentioned is apparent, while 
in the proximal (“‘distal’’) direction, it is very slight. The broad strap-like 
virgula forms a conspicuous ridge-like elevation along the median line, of one 
lateral face, appearing less distinct on the other. Thecz 22-26 in 25™™, 
apparently with the outer wall concave-indented below, and rectangular 
above. Excavation indenting polypary for about one-third of its width, not 
at right angles but inclined (on distal side, of course) about 75° to virgula. 
Young individuals (with a length much less than maximum for the species) 
have, nevertheless, attained nearly the maximum width. 
Horizon and locality.—Upper Dicellograpsus zone, Magog, Canada. 
I at first had a great deal of trouble with the preceding two forms. The 
first light on the subject was obtained by noticing that to my two forms cor- 
responded respectively the two figured at different times by Lapworth under 
the name of Climacograptus caudatus. That they are at least varietally dis- 
tinct there is no doubt. For Lapworth’s caudatus of 1876 (which of course 
remains the caudatus) is about 2™".75 (possibly 3™" ad maximu) wide, has 
only 18 thecze in 25™™, and a more attenuated polypary which enlarges much 
more slowly; while the caudatus of 1877 (var. Zaticaulis) is 3"™ wide (probably, 
judging from my specimens, ad minimum), and has 24-26 thece and a more 
widely obtriangular polypary. Further in var. /atécaulzs the virgula is very 
stout and strap-like, recalling that of Diflograpsis foliaceus. Correlated with 
these differences in theca-numbers and polypary width, is the different pro- 
portions of the ‘“‘denticles.” In cawdatus rhombic, with the ventral and 
apertural margins about equal, in var. Zaticaulis they are considerably wider 
than long. It is possible that the forms are entirely distinct, but the material 
consisting merely of flattened films is not satisfactory on this point. 
