1876.] and Development o/Antedon rosaceus. 213 



in the second * Porcupine' Expedition off the coast of Portugal) ; and I 

 have further information to give on the Rliizocrinus Lofotensis (Sars), the 

 recent type of the Apiocrinida. These, with the numerous other Crinoids 

 collected during the 'Challenger' Expeditiou, will doubtless furnish ample 

 materials for such an elucidation of the Structure and Life-history of 

 this most interesting group as may afford a secure basis for the scientific 

 study of its great Palaeontological series. 



Anatomy. 

 Calyx and its Contents. 



Calyx. — The shallow basin (Phil. Trans. 1866, plate xxxii. fig. 2) which 

 holds the central portion of the visceral apparatus is formed not ouly 

 by the first, second, and third Eadials, but also by the first and second 

 pairs of Brachials, together with the basal segments of the pinnules 

 borne by the second — these portions of the calcareous skeleton being so 

 connected laterally by intervening perisome as to complete the wall of 

 the concavity. This concavity is lined by a smooth membrane, which 

 may be conveniently and, I think, correctly termed peritoneum, as it 

 forms the immediate boundary of the perivisceral cavity or coelom. The 

 calyx is shut in above by the perisome of the oral disk, which is lined by 

 a continuation of the peritoneum; and this is also reflected over the 

 " visceral mass" which occupies the cavity thus enclosed. This " visceral 

 mass" is a compact lenticular body, which includes the whole digestive 

 and sanguigenous apparatus, with the central portion of the circulatory 

 and respiratory systems and the prolongation of the axial cord of the stem, 

 from which is given off the generative rachis that passes into each arm ; 

 but it does not include either what I regard as the nervous centre or 

 the generative organs (testes or ovaries) — the former being contained 

 in the cavity of the centro-clorsal basin which underlies the calyx, while 

 the latter, as has long been known, are distributed through certain 

 pinnules of the arms. 



Oral Dish. — The membranous perisome which forms the oral disk is 

 continuous with that which is prolonged over the oral surface of the 

 arms and pinnules, and which also dips down between the basal segments 

 of the arms to complete the cavity of the calyx. Towards the mouth 

 (Phil. Trans. 1866, plate xxxii. fig. 3), which is situated in its centre, 

 five radial furrows converge, each of them formed by the union of two 

 converging brachial furrows. The distance from the mouth at which thi 

 union takes place is by no means constant ; and I attach little value as 

 a specific character to variations in the distribution of these furrows. 

 The floor of each consists of what appears to be a layer of columnar 

 epithelium, which I believe to be ciliated. Its sides are formed by 

 elevated ridges of the perisome, each of which is scolloped at its edges 

 so as to form a row of minute valvules (the "crescentic leaves" of 



