54 
ANNALS NEW YORK ACADEMY OF SCIENCES 
telasma group, the first pair of septa in the counter quadrants are invariably 
added before the first pair in the cardinal quadrants. 
After finding that the first pair of secondary septa appeared almost simul¬ 
taneously in the counter and cardinal quadrants, the question arose as to 
whether the later pairs of secondary septa were added simultaneously or if, 
during the later development of the individual, the counter quadrants were 
accelerated over the cardinal, and the same condition existed in the mature 
individuals as was found in corallites of other species from higher geological 
horizons. Fourteen of the most perfect individuals obtainable were care¬ 
fully studied and the number of septa in each quadrant counted. These 
individuals were from three or four millimeters up to twelve or fifteen milli¬ 
meters in diameter across the cup and, varying according to size, had from 
three to eight secondary septa in each quadrant. Of these fourteen individ¬ 
uals, eleven had the same number of pairs of septa in the counter as in the 
cardinal quadrants. In the majority of these, the pairs of septa seemed to 
have appeared almost simultaneously in the counter and cardinal quadrants. 
In one or two individuals the cardinal quadrants seemed to be slightly in 
advance of the counter quadrants, and in three or four the counter quad¬ 
rants were distinctly in advance of the cardinal quadrants, although the 
number of septa present were the same in each. The remaining three of 
the fourteen individuals have one pair more of secondary septa in the counter 
quadrants than in the cardinal quadrants. Thus it is seen that on an aver¬ 
age the secondary septa appear almost simultaneously, but that the counter 
quadrants are just a trifle in advance of the cardinal quadrants. The 
smaller tertiary septa appear in the later stages and so far as can be observed 
arise in exactly the same order as the secondary septa, each one taking its 
place between two already existing septa of the primary or secondary cycle. 
This appearance of the pairs of secondary septa simultaneously in the 
counter and cardinal quadrants is a decisive argument in favor of the original 
tetrameral primary condition. If, for the sake of argument, we call the 
pair of septa occurring one on either side of the counter septum primary 
septa, as Duerden and Carruthers 1 have recently insisted that we should do, 
we are confronted with the anomalous condition of having only three of 
the fourteen individuals of Streptelasma profundum above considered with 
the same number of secondary septa in the counter as in the cardinal quad¬ 
rants, and the other eleven individuals would have one more pair of second¬ 
ary septa in the cardinal quadrants than in the counter, a condition exactly 
opposite to that found in any other species of rugose coral. Therefore, it 
seems incorrect to consider any but the first four as primary septa. To 
1 R. C. Carruthers: Annals and Magazine of Natural History, Nov., 1906, pp. 356-368. 
