860 Lindstrdm— On Zoantharia Rugosa. 



areas, and it then continues very nairow and low to the shortest 

 margin. From the highest part of the median ridge two short pro- 

 cesses jut oiit, and embrace a small oval pit, ending at the cardinal 

 margin. This oval pit is often occiipied by the tooth-like portion of 

 the median ridge. The cardinal area is divided by this pit into equal 

 portions covered with coarse and irregular teeth, which diminish 

 in size towards the side corners. On both sides of the median 

 ridge the inner surface is covered with naiTow longitudinal and 

 incurved striaB. 



In one specimen a complete oiDerculum is attached, in another only 

 a fragment of it, but in both cases under very strange circumstances. 

 In the latter specimen the animal began to form a new calyx within 

 the old one (Plate XIV. Fig. 4). This new and narrower calyx 

 consists, as may be seen on the figure, partly of the old walls. It is 

 only towards the bottom surface that new walls have been formed. 

 This new wall, during its growth, coalesced with a remaining frag- 

 ment of the operculum. It is very irregular, parallel with the 

 interior surface of the operculum, and thus is bent in a very sharp 

 fold at the point where the median ridge of the operculum is situated. 

 The new calyx is bent in an irregular arch, and joins the middle of 

 one of the old side walls. It is A'ery evident that no new individual 

 is here formed by means of budding, as the calyx and the walls are 

 quite the same as before, with the exception of that corner. The 

 second specimen, with a complete operculum, shows a distance of ten 

 millims from the apex of its largest surface, another of a different 

 kind, which meets the former at right angles, and is separated from 

 it only by a narrow fissure. On closer inspection this surface is 

 found to be an operculum left behind in its old place, while the animal, 

 as in the case before cited, was reducing and diminishing its volume 

 and partly formed a new calyx within the old. The new walls 

 grew all round the operculum, which exactly resembles, in its lines 

 of growth and shape, detached opercula of the same size. Those 

 parts above and around the operculum have by no means resulted 

 from budding — ^it is only the bottom surface which is interrupted in 

 its growth ; the others continue as before. Moreover, the budding 

 seems to be a very rare mode of propagation in GoniopJiyllum, and is 

 only seen in large individuals where the young shells, as in Oyatho- 

 phjllum, are placed on the highest rim of the calyx. There is no 

 reason to suppose that these phenomena of the reduction of the size 

 are mere monstrosities, as they are also observed in numerous other 

 specimens of Gonio'p'hijlhhm, and frequently in Z. rugosa. This pecu- 

 liar formation of a new calyx within the old is common to almost 

 all individuals of Z. rugosa, and is repeated several times by the 

 same individual, as, for instance, in ChonopliyUum, when the shell 

 resembles a number of funnels placed within each other. It may 

 then, as in GoniopJiyllum (and as will also be shown in Calceola Goth- 

 landica), be presumed that the animal, at the time of these restrictions, 

 commonly lost its old operculum, now too large, and formed a new 

 one, although it was sometimes left attached, in consequence of the 

 ligament decaying less rapidly than usual. Those species again which 



