408 Lindstrom — On Zoantkaria Rugosa. 



other bodies (Plate XIV. Fig, 14). The apex of the young shell 

 seems actually to shoot forth from the shell-matter of its parent, 

 generally from a groove between two vesiculas. If the embryo had 

 fixed itself, when the shell became empty after the death of the 

 parent animal, it could not, of course, have penetrated in this 

 manner the mother shelL 



The characteristic shape of the Calceola is distinct in specimens 

 of a length of three millims. They are connected with the large 

 shell by small rootlets, as well as by their first point of attach- 

 ment. There is commonly but one bud, seldom one in each comer, 

 more rarely two in each, and only in one instance three on each side. 

 In a specimen of seven millims in leng-th there are already two small 

 buds, they all start from the same point, following, during their 

 course, different directions, generally upwards, but also towards the 

 sides and downwards. Such small shells, as are found attached to 

 other bodies, must have originated in the common manner by the 

 extrusion of free swimming embryo from an ovum. As no aggre- 

 gate gi'oups of individuals are found, it is probable that the buds 

 ha^'ing gained a certain size, became free. As to the interior structure 

 of the shell, it consists of basin-shaped layers of oval vesiculas (Plate 

 XIV. Fig. 18), enclosed by a thiii exterior coating, formed by the 

 septa, and consisting of narrow longitudinal stri^. 



The operculum of this shell is quite as semicircular as the mouth of 

 the calyx (Plate XIV. Figs. 15 and 16). It has only once been found 

 attached to its shell (Plate XIV. Fig. 13), although it cannot be con- 

 sidered very rare. The outside is marked by faint longitudinal strige 

 and concentric lines of growth. The nucleus is central and projects in 

 a small point. It is cii'cular, in accordance with the cylindrical form 

 of the smallest shells, which soon become flattened on the side upoii 

 which they rest. The operculum is thickest in its centre, and con- 

 vex on the outside, the interior smface being slightly concave. The 

 uppermost edge, or what may be called the cardinal margin, is much 

 thicker than the very thin or rather sharp side margins. . Although 

 thick, there is no such regular area at the cardinal margiri, as in 

 Calceola sandalina. On the interior side (Plate XIV. Figs. 16 and 17) 

 there is, in the centre, a narrow longitudinal ridge, which disappears 

 almost before it has half reached the inferior margra. It is largest 

 and highest at a distance of two millims from the cardinal margin, 

 where it also ends. Above is a small oval pit, enclosed by two pro- 

 cesses, which originate in a common point on the cardinal margin ; 

 they also embrace the median ridge. In addition to this, the interior 

 sm'face is covered with 18-20 stride on each side of the median 

 ridge, curved ia an arch towards it. They are arranged in pairs, 

 but each ray has its distiact starting point at the cardinal margin, 

 parallel to which runs a shallow grove, only interrupted by the oval 

 pit before mentioned. 



The operculum in this species was also deciduous, but neverthe- 

 less some specimens show that it continued its function during 

 the reduction of the shell. Some opercula are extremely thick, with 

 the interior or yoimgest stratum far less extensive than the next 



