GEAF ZU SOLMS-LAUBACH— MONOGRAPH OF THE ACETABULAIUE.E. 21 



C. Disci fertilis radii liberi, iuterdum incrustationc plus minus coaliti. Corona 

 inferior nulla. Coronie superioris processus inter se liberi. {Pobjphysa.) 



1. Radii omnino liberi, incrustationc nulla vel subnulla, aequali. 



a. Radii vesiculiformes, obtusi. Processus coronse pilis binis oblique seriatis 



instructi 11. A. Peniculvft. 



/3. Radii sursum curvati, elougati, apiculati. Processus coronas pilis ternis 



triangulariter dispositis instructi . . 12. A. exigua. 



2. Radii incrustatione partiali laterali coaliti. 



a. Processus coronae pilis ternis instructi 13. A. parvula. 



y3. Processus coronae pilis pluribus instructi. 



* Pili circulariter dispositi 15. A. Mohii. 



** Pili elliptice dispositi 14. A. pohjphysoides. 



Section I. Acetabulum. 

 Fertile disc composed of rays firmly united up to their tips, and liavini^ corona superior 

 and inferior likewise laterally united, with ovate spores. 



1. AcETABULAEiA MEDiTEREANEA, Lam. Hist. Polyp. corall. flex. 183 6, p. 249. 



Disc in fully developed state extended flat, when younger more or less concave ; 

 sporangial rays as it w^ere cut off straight at the tips, with much thickened, completely 

 united membranes; corona superior forming a circular continuous undulating ring 

 surrounding the apex of the disc and corresponding wdthout and within to the narrow 

 individual coronal rays. Hairs or hair-scars on the apical surface of the coronal rays in 

 a single row in greater numbers (5-7), generally in tufts; corona inferior of similar 

 form, its rays in the apical view being notch-like at their outer margin. 



Size of normal specimens : diam.*of disc 10-12 mm., often much smaller : breadth of 

 corona superior circa 0'125-0'150 mm. ; longit. diam. of spores, circa 0'095 mm., transv. 

 diam. 0-07 mm. (Plate I. figs. 4, 5, 7, 8, 12.) 



This species, w^hich is among the largest of the genus, is easily recognized by the 

 characters of the section Acetahultmt. Its mode of calcification has been closely studied 

 by Leitgeb. Its degree varies very greatly ; the calcification of the peripheral layers, 

 which is excessive in sunny localities, may be completely wanting at greater depths or 

 in shadow. The specimens then appear quite green. 



Section II. Acetabuloides. 

 Sporangial rays more or less firmly united or completely or partly free; corona 

 superior and inferior present, both consisting of free processes not united laterally with 

 each other. 



A. Side-walls of the sporangial rays notched together by distinct thick processes reaching from the 

 upper surface to about the middle, gradually running out and springing towards the middle lamella. 

 The largest species of the genus. 



a. Sporangial rays with apiculum and with the process of the corona superior bilobed outwards. 



2. Acetabularia Kilneri, Ag. Till Alg. Syst. viii. 1880, p. 171. 



Pertile disc large, long-stalked, only terminal, extended flat or slightly infundi- 

 buliform upwards, moderately calcified. Sporangial rays (57 in number) firmly united 



