438 R. G. Garruthers — Remarkable Carboniferous Coral. 



observation. From now onwards, however, the addition of new septa 

 follows a definite plan. Let the five-septal stage be provisionally- 

 regarded as primary : on inspection it will be noticed that two of the 

 septa are set out from the epitheca more closely than the rest 

 (i.e. those lettered CL in Figs. 1/ and 3f, PI. XI), an arrangement 

 emphasized in later stages. Using the terminology applied to normal 

 Rugosa, these two septa, throughout the metaseptal stages, behave as 

 if they were the counter-lateral primaries, the septum directly opposite 

 as if it were the main (or cardinal) septum, the remaining two as if 

 they were the two alar primaries (cf. Diagram and PI. XI) ; that is 

 to say, once the five-septal stage is completed, of all septa appearing 

 in the sectors A-H the last-formed is the one nearest to what, for the 

 sake of argument, has been termed the main septum H ; in the two 

 sectors A-CL the youngest septum is the one closest to A. 1 It is 

 obvious that such an arrangement is strictly in accordance with that 

 governing the insertion of metasepta for the Rugosa in general. This 

 is satisfactory enough, but there still remains one respect in which 

 Cryptophyllum shows a remarkable divergence from the normal. It 

 will be seen, on referring to the serial transverse sections la— If, 

 PI. XI, that in not one of these, not even in those of the final growth 

 stages, can any trace of a counter primary septum be detected : yet 

 in other Rugose corals, this would have been present throughout, 

 from the earliest stages onwards. The omission is at first puzzling, 

 but a clue is obtained in the next set of serial sections (PI. XI, 

 Pigs. 3a-3h), cut from what is apparently a more advanced type : 

 here, in the final section, 3h, a single septum (lettered G), relatively 

 small, at last appears between the two counter-laterals CL. The 

 same thing happens in another set of serials (PI. XI, Pigs. 2a-2c). 



The conclusion that the septum which appears so tardily between 

 the two most closely approximated of the five primaries of 

 Cryptophyllum, is in reality the missing counter-primary, is 

 confirmed by the study of one more set of serials (PI. XI, Aa-d). 

 In these it will be noticed that in the final growth-stage (Fig. id) 

 two new septa, quite small, have come in, one on each side of the 

 " counter septum ". In an early paragraph of this paper, it will 

 be remembered that when commenting on the scheme of septal 

 development characteristic of Rugose corals it was stated that the 

 minor septa " are relatively short, and are most often a feature of 

 adult growth-stages", and that "sometimes there are two minor 

 septa only, in which case they are restricted to the two counter- 

 lateral sectors, one on each side of the counter-primary G ". If, 

 therefore, the two small septa, one on each side of G in Fig. 4d, 

 PI. XI, be regarded as minor septa (which their appearance at such 

 a late growth-stage would indicate), all difficulties vanish : their 

 development agrees with that characteristic of minor septa in other 

 Rugose corals, and supports the conclusion arrived at on other 

 grounds, that the septum G is in reality the counter-primary. 



1 Naturally this cannot be fully demonstrated in the sections figured, but it 

 has been confirmed by the examination of specimens from which the epitheca 

 was removed by acid. 



