Lindstrom — On ZoantJiaria Rugosa. 357 



cellular or vesicular structure ; there is another peculiarity as yet 

 not much known. ^ 



Several Bugosa are provided with an operculum of very strange 

 shape. Guettard'^ first made known the occurrence of such an 

 operculum, and, later, Steenstrup saw it in a Cyathophyllum mitratum. 

 But as several of these operculated fossils have been placed with the 

 BracMopoda and other classes, it is necessary to give a detailed 

 description of the species, in order that their true affinity with 

 Bugosa may be demonstrated. 



The TurbinoUa pyramidalis, Hisinger, from Wisby, Isle of Grotland, 

 is, perhaps, the most remarkable form of all. Girard^ considered it 

 to be a Galceola, but his view was rejected by MM. Edwards and 

 Haime,* who placed it in their genus Goniopliyllum. 



The shell, or the polyparium, as it is also, named, is in its exterior 

 shape irregularly pyramidal, with four triangular surfaces of unequal 

 size. The largest, or the bottom surface, is that on which the shell 

 rests when in its natural position. The lateral surfaces are some- 

 what smaller, and the uppermost surface is the least. The apex 

 is generally sharply bent towards the smallest surface, just as in the 

 common hornlike forms of the Gyathaxonm and the Zaplirentince. 

 as well as in the Cyathopliyllince and Cystiphyllidce. The four corners 

 where the surfaces meet are rounded and grooved by a peculiar 

 shallow furrow. The lines of growth continue uninterrupted on all 

 the surfaces, and between them are extremely thia parallel striee. 

 They are crossed by numerous faintly elevated strise, which are 

 homologous with the much more prominent folds (the " false 

 costoe " of the OmpJiymcs, eto.y 



The two middle folds, which divide the surface in two parts, are 



1 "With very few exceptions, as in Actinia plumosa, of Torell, the calyx oi Aeii- 

 nozoa may be divided into two exactly similar parts by any diameter whatever. The 

 Rugosa, on the contrary, are only to be divided into two equal parts by a line drawn 

 along the longitudinal axis of the septal pit, or the largest of the four primary septa. 

 M. Ludwig (in Meyer's Palseontographica, Vol. x. p. 179) has ranged some of the 

 Cyatliophylla amongst the Aporosa, and formed a distinct family of the Zaphrentin« 

 called Finnatce. Although his own figures show that their septa are developed accord- 

 ing to a quarternary system, he presumes that the "tentacula" and the primary 

 septa have been originally six, and considers the other great differences from the 

 Turbinolidce as of no value. 



2 Memoires, Tome iii. p. 516. 



3 Leonh. and Bronn, Jahrbuch, 1842, p. 232. 

 * Archives du Museum, Vol. v., p. 404. 



s In all the specimens of Z. rugosa these " costce" alternate with the septa, there is 

 no immediate continuation of these through the walls of the calyx as in the Z. aporosa 

 ani perforata. On the exterior wall the furrows between the longitudinal folds are 

 opposite the septa. As above described in Goniopliyllum two or three broad longitu- 

 dinal folds or strioB are also seen, in most of the Rugosa, to divide the longest side of 

 the shell in two similar parts and to form a ridge, which, as I shall endeavour to 

 demonstrate, is homologous with the pseudo-deltidium of Calceola, The largest sep- 

 tum (or the septal-pit as seen in so many of the Zaphrentince) is situated on the 

 interior wall opposite the furrow between these larger median folds. The smaller 

 folds converge towards these median ones in a very acute angle, and the whole thereby 

 takes a pinnate arrangement, as J. Hall has described it in Streptelasma corniculum 

 (Pal. of New York, Vol. ii. p. Ill), and F. Eoemer in 5. europceum (Foss. Fauna von 

 yudewitz, p. 16); see also Ludwig. 



