ON th;e genus alteolites etc. 367 



process in different tubes, by its often extending ]aalf way, or 

 almost quite, across the visceral chamber, and by its absence in all 

 but a comparatively small number of corallites, and those the 

 largest ones. Upon the vrhole, therefore, we.are inclined to be- 

 lieve that the tooth-like processes of A. septosa, A. depressa, and 

 Chcetetes radians are not of a septal nature at all, but^that they owe 

 their existence to fission taking place in the older corallites. 



In the third place, all the three corals in question exhibit the 

 peculiarity that the walls of the corallites are firmly amalgamated 

 in contiguous tubes, so that a fracture does not expose the walls 

 of the tubes, but lays open the cavities of the visceral chambers. 

 Mr, Lonsdale probably attached too great a value to this character 

 in regarding it as one of the leading peculiarities of Chcetetes as a 

 genus ; but there can be no doubt that it is a feature of importance. 



Upon reviewing all the above evidence, it seems to us to be clear 

 that A. depressa, Flem., and A. septosa *, Elem., can no longer be 

 retained in the genus Alueolites as typified by A. suhorhicularis 

 and its allies. On the other hand, if more extensive investiga- 

 tions confirm, as we believe they will, the absence of mural pores, 

 these species must be placed in the genus Chcetetes, side by side 

 with C. radians, Fischer, and they will stand as C. depressus, Flem ., 

 and C. septosus, Flem. 



Group E. Ch^tetes, Fischer. 

 The groups known as Chcetetes, Fischer, Jfb?^/^>^*Z^j3or«,D' Orb., 

 and Stenopora, Lonsd., differ from Favosites emd Alveolites mainly 

 in the imperforate condition of the walls of the corallites ; and this 

 undoubtedly constitutes a character of great structural importance. 

 Owing, however, to the very small size of the tubes of many spe- 

 cies of these groups, the absence of mural pores is often a matter 

 more of inference than of actual observation. "Without, however, 

 entering at the present moment further into the structure and 

 affinities of these groups, we wish to describe a species of Chce- 

 tetes from the Carboniferous rocks of Scotland, which is in many 

 respects allied to the forms we have just been considering : — 



Chcetetes hyperboreiis, Nich. & Eth, 

 Corallum forming thin, flattened, or undulating expansions, from 

 one to five lines in thickness, not composed of superposed layers, 

 and often half a foot or more in diameter. The corallum is not 



* It should be noted that this species was long ago described by M'Coy undejr 

 the name ChcBtetes septosus (Pal. Foss. p. 82). 



LINN. JOUBN. — ZOOLOGY, VOL. XTII. 31 



