48 EOCENE AND LOWER OLIGOCENE CORAL FAUNAS. 



septal loculus. The granulations that go to form syuapticulse are iisuallv 

 more enlarged than the otlier granulations. Pratz recognized two different 

 types of syuapticuhv, leasing their differentiation upon whether two granu- 

 lations fuse directly across the interseptal loculus or whether a new center 

 of calcification is introduced to effect the junction. To the former kind he 

 gave the name false or i)seudosynapticula?, and to the latter true syuapticulse 

 or simply synapticulae.' Much has been written about the validity of this 

 distinction and its systematic value. PI. II, fig. 1, represents a section of 

 Siderastrea copied from Ogilvie (op. cit., fig. 71, p. 244)." Whether 

 syuapticulse are true or false seems to depend on spacial relations within the 

 interseptal loculi. If the septa are crowded or near their inner margins 

 where their surfaces are close together, the opposed granulations can fuse 

 directly, one to the other; but if the two opposed septal faces are somewhat 

 remote, additional calcification centers are needed to effect the fusion. The 

 figure of Siderastrea shows this well.^ (See PI. II, fig. 1.) 



Therefore, in my opinion, whether syuapticulse are true or false is of 

 no special systematic importance. 



THE WALL (THECA). 



The wall of a simple coral or of a corallite of a colony is that part of 

 the skeleton that cuts off more or less completely the interseptal loculus 

 from peripheral^ commiuiication witli the outside. 



The minute structure of the walls of corals is of very many types. 

 The oldest type is where the ends of the septa did not fuse distally, but 

 simply had their outer ends bound together by an epithecal covering.* 

 The figure of Bhedopsammia daibornensis (PI. XXI, figs. 12 and 13) shows 

 that this coral passes tlii'ough this stage in its early development (the basal 

 plate and epitheca being considered as homologous). 



The next type of wall may be considered the pseudotheca of von 

 Heider.^ This is formed by the septa becoming distally so much thickeued 



1 Op. cit., p. 9 (Vol. XXIX, p. 89). 



-For criticisms on tbis subject, see Bernard, Geol. Mag., Mar. ami Apr., 1897, p. 176; and 

 Vaughan, Bull. Mus. Comp. Zool. Harv. Coll., Vol. XXXIV, 1899, p. 248. 



■'Von Koch in his Das Skelett der Steinkorallen, p. 260, says in a footnote: "Das Vorkommen 

 von iichten und uniichten Synapticnla zwischen denselben Septen wurde von mir bei Fiingia nacbge- 

 wiesen (Fig. 7). Aus dicser Figurliisst sich auch erseben (Fig. 3b), dass blosse Hockerchen der Septen 

 ein eigenes Krystallisations-centrura besitzen konneu." (Morph. Jabrb., Vol. XVI, 1890, pp. 687-688.) 



■iSee Ogilvie, op. cit., p. 218, lig. 72. 



'Arbeiten aus dem Zoiilog. Inst, zu Graz., Vol. I, No. 3, 1886, p. 178. 



