36 



NATURE 



[May 10, 1883 



corallum is very much like that of Calceola in shape, but 

 more elongated. It may be simple or form large masses 

 by two modes of budding — either calicynal budding, or 

 budding from the abundant rootlets. In the specimen of 



Fig. l.—Rhizsphyllum clongatitm. View of the interior of the calicle to 

 show the six young calicles developing as buds within it. 



Rhizophyllum here figured, six young corals are seen in 

 the act of developing as buds in the interior of the calicle. 

 In consequence of budding taking place from the 

 "rootlets," the author advances the new suggestion that 

 these bodies, the nature of which has always been doubt- 

 ful, are to be regarded as stolons. The operculum of 

 Rhizophyllum, by which the mouth of the calicle is com- 

 pletely closed, is, as in Calceola, of a semicircular shape, 

 with a prominent ridge-like median septum on its inner 

 face. In Rhizophyllum atteuuatum, a compound form 

 from Louisville, in Kentucky, first described by Mr. V. 

 W. Lyon under the genus Calceola, the stolon tubes 

 partly serve to connect together adjacent calicles, partly 

 become themselves developed into fully-formed calicles. 

 Specimens of Rhizophyllum Gothlandiatm are found in 

 abundance in the Island of Gothland with their opercula 

 detached. The separate opercula are also common ; 

 specimens with the opercula in situ are comparatively 

 rare. A remarkably perfect one is shown in the accom- 

 panying figure. 



Fig. 3. — Rhizophyllum elongation* View of the calicle with the operculum, 

 a single valve only in situ. 



The second group of the Calceolidae contains only a 

 single genus — Goniophjllum — in which the mouth of the 

 calicle is rectangular in form, and four opercular valves 

 are present which, with their bases resting on the four 

 sides of the mouth of the calicle, slope inwards to meet 

 one another, and form a four-sided pyramidal roof over 



Fig. ^.—ConiophyUnm pyramidale (mulatto prima). View of the mouth 

 of the calicle, with the opercular valves in situ, the dorsal right and left 

 valves being entire, the ventral incomplete. 



the calicle. From Gothland Prof. Lindstrom has been 

 able to obtain two or three specimens with all the four 



opercular valves in situ. So that doubts as to the connec- 

 tion of the valves with the coral calicle are now inad- 

 missible. On careful study of these specimens and 

 numerous others with a fewer number of valves in situ, 

 he finds that the four valves always present well-marked 

 differences and form, and septal striation, so that it is pos- 

 sible to distinguish with certainty an anterior and posterior, 

 or ventral and dorsal, and a right and left valve, and pick 

 these out from any collection of well-preserved loose valves. 

 The anterior and posterior valves are trapezoid in form, 

 the lateral triangular. A most remarkable discovery he 

 has made is that these corals must have shed their valves 

 periodically, and replaced them, and that when shed the 

 valves frequently happened to become attached to the 

 wall of the calicle, and fused with it. In the accompany- 

 ing figure of Goniophyllum pyramidale, seen from behind, 

 a well-formed operculum is seen near the base firmly 

 attached to the wall of the calicle near its base. Such 



FlG. 5. — Goniophyllum pyramidale, viewed from the ventral side to show 

 the shed opercular valve (a) coalesced with the wall of the calicle near its 

 base. 



specimens are not uncommon in Goniophyllum, but in 

 another genu;, a new one, Araeopoma, belonging to the 

 second family of operculate coral, devoid of a median 

 septum, and which has four triangular valves like Gonio- 

 phyllum, very many specimens bear numerous valves 

 fused to their outer walls, the valves being of increasing 

 size from below upwards, in accordance with the growth 

 and expansion of the coral and the mouth of its calicle. 

 In one abnormal specimen of Goniophyllum pyramidale 

 there are five opercular valves present, a minute extra 

 triangular valve being interpolated at one of the corners. 



Prof. Lindstrom, whose important researches on the 

 development of the septa in so-called Rugose corals are 

 familiar, has been able to trace the development of the 

 corallum in Goniophyllum pyramidale. He finds that in the 

 youngest stage of the calicle there is no septum present at 

 all, then that one septum is formed on what may be termed 

 the dorsal side of the calicle, and since in this genus and 

 several others it remains conspicuously prominent, it may 

 be termed the primary septum. Two further septa, the 

 light and left median, are next formed, and last of all 

 the ventral septum, long after the others. He points out 

 that a similar process of development is followed in most 

 Rugose corals, and that it is therefore erroneous to treat 

 of four septa as primary in these forms. 



In Rhytidophyllum shaped somewhat like Calceola, but 

 belonging to the Araeopomatidae, by reason of the absence 

 of a defined median septum on the operculum there is 

 only a single opercular valve. A further genus of the 

 group is possibly represented by a single broken oper- 

 culum, of which further specimens have not yet been 

 found. 



In connection with the operculate corals, Prof. Lind- 

 strom describes certain coral forms in which remarkable 

 exothecal structures are present, which maybe considered 

 as more or less homologous with opercular valves. In 

 Pholidophyllum iubulatum, a compound coral, first de- 

 scribed as Tubiporites tubulaius by Schlotheim in 1813, 



