DESCRIPTIONS OF SPECIES. 129 



the septa are short, only a few dentations are seen. In this species the 

 presence of more than ten septa is rare. But occasionally there are rudi- 

 mentary septa of a higher cycle in a few interseptal loculi, as Gregory found 

 to be the case in M. decactis^ (Lyman). The general features are the same 

 as in M. ganei. Frequently between the outer septal ends there is a 

 slight bulging inward corresponding to the intervening true thecal calcifi- 

 cation centers. These slight projections should probabl}^ be considered very 

 rudimentary septa. 



The resemblance of M. mirabilis (D. and M.) to M. ganei is remarkably 

 close considering that they are so widely separated in geologic time. 

 The two species are, however, specifically quite distinct; they only belong 

 close together in the same genus. The calices of mirabilis are only about 

 1.5 mm. in diameter, while the smaller calices of ganei usually measure 2 

 mm. There are other differences also. Quite frequently rudimentary 

 smaller septa exist in mirabilis between the larger septa. The inner part of 

 the septal margins is dentate, but the part that is exsert has an entire 

 margin: with a hand lens no dentations could be detected. 



Fowler^ has published some very interesting notes on Madracis asperiia. 

 Although it is a digression to introduce them here, it may be permis- 

 sible. The more salient points are: The tentacles are both ectocoelic and 

 entocoehc; the septa occur between pairs of normal mesenteries; the 

 directive mesenteries are well developed, but do not (as is the case in 

 Pocillopora and Seriatopora) always coincide with the axial and abaxial 

 plane of the branch; there are peripheral lamellae of the mesenteries in 

 areas immediately surrounding the polyps. Von Heider has published an 

 interesting paper, '' Mudracis pharensis Heller," in which notes are made on 

 most, if not all, of the then known species of the genus.^ 



MADRA.CIS .JOHNSONI sp. IIOV. 



PI. XIII, figs. 8 to 11. 



Form ramose; large, thick, compressed branches; surface granulate; 

 no costfE. Sometimes longitudinal, elevated, more or less granular lines. 

 Cahces with a more or less spiral arrangement; sometimes decidedly spiral. 



'Quart. Jour. Geol. Soc. Loudon, Vol. LI, Aug., 1895, p. 258, fig. 1. 

 2 Quart. Jour. Microsc. Sci. (N.S.), Vol. XXVIII, No. Ill, Feb., 1888, pp. 4U-416. 

 ^Koralleustmlien, Arbeiten aus d. ZoiUo};. Institut zu Graz: Zeitsch. fiir wiss. Zoiilogle, Vol. 

 LI, 1891, pp. 316-31'2, pi. xxiv. 

 MON XXXIX 9 



