64 



S. LOVEN, ON POURTALESIA, A GENUS OF EPHINOIDEA. 



as typically composed of a central ossicle, five costals, and five radiah. *) I shall make 

 use of the same terms here, without fear of being misunderstood. When future science 

 siiall have lying before her, for comparison, numerous forms now undiscovered, and the 

 perplexities of the present shall have cleared up, the final terminology will come of 

 itself. ') 



What the calyx is to the antique Crinoid, its licmologon is not to the Echinoid, 

 — its constituents were iidierited morphologically, not their modes of subserviency 

 to the physiological activities of the animal — ; along with the enormous change in 

 conditions of existence there have arisen essential alterations of the entire structure. 

 In the Crinoid, as in the Echinoid, the calyx is noi'mally opposite to the mouth. In 

 the stalked Crinoid, which feeds by means of ciliary agency, the mouth is directed 

 upwards, and the calyx, on the darkened side, is the fundamental support on which 

 the body rests, permanently or temporarily, enclosed on all sides by its perisome, 

 with its radiating grooves. In the Echinoid, when first seen by us already long since 

 adapted to a free and ground-feeding life, with the mouth directed downwards, the 

 calycinal system, permanently adnate, is carried uppermost, towards the light, on the 

 top of the back, and there, covering probably the dorsal part of the perisome, nor- 



oOg> 



Cyathocrinna alutar-cus 

 Ang. 



Tiarechiuus priuceps 

 Laubk. 



Salenia sp 



Cidaris Mercevi 



COTTEAU. 



mally meets the ambulacra radiating from the mouth, at their growing extremities, 

 but never lifts or supports them. ^) In consequence of the thus inverted posture, 

 the inner organs of the Echinoid are to a great extent transposed and brought in- 

 to relations to the calycinal system widely contrasting with those existing in the 

 Crinoid. Relatively to the other skeletal constituents the calyx holds its legitimate 

 position, but under it, owing to altered conditions, an assemblage is brought together 

 of organs of primary importance: those of vision, — apparently foreign to the Crinoi- 

 dean type, at least not to be looked for in a homologous place — , those of generation, 

 of aqueous circulation, and of excretion. And thus, in the Echinoid, the calycinal system 

 is rendered, to no small extent, a disputed ground, each of these organs tending to 

 penetrate its substance, and to gain access to the surrounding water. 



Of all the Echinoidea at present known Tiarecliiiuis has the most antique looking 

 (;alycinal system, /-"/. XIII. It is large enoiigli to cover the gi'eater part of tlie dorsal 



') Etudes p. 73. 



-) It is well known that Miller was inconsistent in tlie use of tlie (cnn "costalsu, hut it has always been 



considered allowable to sug!i;est the use in a strict sense (if a term elsewhere vaguely applied. 

 '^) Etudes, 1. c. 



