46 EOCENE AND LOWER OLIGOCENE COIIAL FAUNAS. 



Miss Ogilvie lias divided sejjta, accordiug to tlieir ornameutation, into 

 two classes — (a) striated septa; (b) ridged septa. The descrijitive terms 

 indicate the character of the ornamentation. The striae or tine lines on 

 Turbinolia, Eupsamniia, and some other septa (see Trochocyathus hmuUti- 

 formis, PI. VII, iig. 4; D'lscoirochns orhif/tiianus, PL V, fig. 19a; and description 

 of Dichocoinia stokesi, p. 14U) are due to simple trabeculie, which often have 

 elongate g-ranulations placed along their courses. A particularly good illus- 

 tration of a striated septum is TrochosiuUhi ////// Vaughan.' Ridged septa 

 are due to the septa being composed of compound trabecula-. Such a 

 trabecula is thicker along its axial portion and thinner on the sides. The 

 result is a ridge of greater or less width, corresponding to that of the com- 

 pound trabecula. The graimlations of such a ridge follow the distribution 

 of the calcification centers. The genus Mussa is a good illustration of septa 

 of this class. Attention is especialh' called to (_^gilvie's work alreadv cited. 



The striaj or ridges present different characters in different corals. 

 They may vary in the sharpness of the summit and also in Avidth, and stride 

 may be opposite or alternate in ])osition. Simple d(iscriptive adjectives 

 readily suggest themselves for the characterization of these features. 



(3gilvie does not take into consideration all of the classes of sejita that 

 may be recognized. In Paracyathus, for instance, though the septa show 

 striaj around their upper edges and enable one to discover the direction of 

 the trabecular, deeper down in the corallum the granulations have fused 

 from one trabecula to the next to such an extent that thev are often 

 connected and arranged in curves j^arallel to the septal margin. (See 

 Paracyatlms helhis, I'l. VIII, fig. 20.) A good descriptive term fm- sucli 

 septa has not suggested itself. 



The ornamentation of the septal faces of Haimesiastra'a (PL XVI, fig. 4) 

 is peculiar. There are no granulations and no raised stria', but gentle undu- 

 lations that cross tlie ti'abeculae. 



PALI. 



Pali are lobes or teeth occurring on or near the inner ends of septa, 

 and possess some recognizable differentiation from the main body of the 

 septum. Trochoci/afhus lunulitiformiH, PL VII, figs. 4 and 8; T. hiiatli, PL VI, 

 fig. 20; Paracyatlms aUernatus, PL VIII, fig. 11a; CaryophyU'td da/li, PL IX, 



I Bull. Mus. Comp. Zool. Harvard Coll., Vol. XXXIV, 1899, p. 233, pi. xxxvi, fig. 4. 



