422 Reviews — Dr. F. A. Bather — Cystideans froTn Girvan. 



a subvective system of ciliated grooves/ and he shows that each of the 

 elliptical organs was in part such a groove ; that the rim is divided 

 at about two-thirds the distance from its outer end into an inner 

 short U and an outer lonff U, meeting by their free ends. The opening 

 of the larger U was roofed in by an alternating series of movable 

 cover-plates, and the opening of the short U was protected by its 

 own bounding wall so as to form a hood which on occasion could 

 meet the closed cover-plates, and so shut the whole opening. " Every 

 known Echinoderm with a stem is a Pelmatozoon, and as such obtains 

 its food by a subvective system of ciliated grooves, there is therefore 

 no reason to suppose that in this respect Cothnrnocystis was any 

 exception. . . . When in full swing the cover-plates v/ere open, the 

 tentacles or podia were fully protruded, and a stream of sea-water 

 was driven down each of the fifteen or more grooves, and diverted by 

 the hood of the short U through the round mouth. Then if some 

 passing animal brushed against a tentacle, the podia were quickly 

 retracted, all the cover-plates shut down, and the hoods pulled up 

 against them so as to close the mouths." (p. 415.) 



In what position did Cothurnocystis live ? There is no trace of 

 a root or of any means of attachment, and it is probable that the 

 stem after gradually tapering was rounded off abruptly, and did not 

 fix it in any way. The position of both intake and vent are on the 

 obverse face ; we may conclude, thei'efore, that the reverse face was 

 directed towards the sea-floor. The extreme flattening and lateral 

 extension of the theca lead to the conclusion that the whole skeleton 

 lay flat on the sea-bottom. The knobs on the reverse side of the 

 frame and the strut on that side served to give support to the flexible 

 integument. 



Remarkable as this form appears to be among the Cystidea, it is not 

 alone, for C. curvata (save in the absence of the club-shaped spines 

 upon its dorsal surface) is a near repetition of this prolate type (see 

 text-figs. 24, 25, op. cit., p. 409), and Ceratocystis Perneri, 'Jaekel, 

 from the Middle Cambrian of Bohemia, is also remarkable for its 

 boot-like form (see p. 423, text-figs. 33, 34). 



The Pelmatozoan life was a very simple existence : its members 

 were mostly sedentary (if not always attached), receiving their food- 

 particles along specially constructed food-grooves, subsisting, like their 

 neighbours the Protozoa, Brachiopoda, Lamellibranchia, and Tunicata, 

 on the currents made by their podia or cilia in the sea, which with 

 its stream brought them the needful supply of aliment. Many of the 

 more energetic members of the Eleutherozoa (the sea-urchin, starfish, 

 and sea-cucumber) indulge in a predaceous and peripatetic existence, 

 filling their stomachs with a selected and more attractive diet. 



But we have already trespassed upon our allotted space, and can 

 only refer to the ingenious explanation of the author (pp. 415-17) to 

 show how Colothnrnus, with the help of its short stalk, its flattened 

 body, and its rigid frame, furnished with knobs and spines, sustained 

 life by lying flat upon the sea-floor, and through all its vicissitudes 

 always managed to keep its right side 7ip. 



^ See PI. XIII, Fig. 1 (a line of fifteen elliptical openings parallel to the 

 marginal plates 5-7) . 



