320 Renews — Waclismuth ^ Bpnnger''s Monograph on Crinoids. 



The columnal that remains thi'oughout life at the proximal end 

 of the stem in the Ichthyocrinidse and their allies, as well as in 

 the Apiocrinid^ and their allies, may also fuse with the infrabasals, 

 but is in other respects hardly comparable with a true centro- 

 dorsal, though often called by that name ; it is therefore convenient 

 to distinguish this as the ' proximale.' ^ 



The teg-men, or ventral covering of the calyx, consists of orals, 

 ambulacrals, and interambulacrals. Through some portion or other 

 of the tegmen there are pores, which place the outer water in 

 communication with the body-cavity, and so, indirectly, with the 

 water-vascular system. In most recent crinoids these pores are 

 scattered over the tegminal surface and penetrate the plates of 

 which it is composed. According to the work before us (p. 35), 

 "the perforated plates have received the name an- ambulacrals.''^ 

 This does not represent fairly the accepted use of the word 'anam- 

 bulacral,' and is sure to perplex the beginner. The term was 

 invented by Joh, Miillei', who applied it primarily to the above- 

 mentioned water-pores, to distinguish them from the ambulacra! 

 pores for tube-feet (podia). The term has, however, been extended 

 not merely to the plates pierced by the pores, but to the remaining 

 imperforate plates of the tegmen other than ambulacrals or covering- 

 plates and adarabulacrals or side-plates.^ In fact, rightly or 

 wrongly, ' anambulaci^al ' is nowadays a synonym of the less 

 ambiguous ' interambulacral,' and should either be dropped or 

 redefined in the strict Miillerian sense. It cannot well be extended 

 to all perforate plates, for some of these may be actual brachial 

 elements. 



The term 'adambulacral ' has just been mentioned. Messrs. 

 Wachsmuth and Springer write (p. 36): "The ambulacral plates 

 consist of the ad-ambnlacral or side-pieces, and the covering plates, 

 or Saumpldttchen ; the former, when present, constitute the outer, 

 the latter the inner rows of the plates." It seems to me more 

 precise and more in accordance with the use in other Classes of the 

 Echinoderma, to restrict the term ' ambulacralia ' to the alternating 

 covei'ing-plates, and not to widen its connotation so as to include 

 adambulaci'alia. It must be admitted, however, that it is often hard 

 to distinguish side-plates from covering-plates, owing in some cases 

 to the conjpound structure of the latter, in other cases to their partial 

 or complete atrophy. 



The use of the word ' ambulacra ' also appears to me highly 

 incorrect. " The ambulacra," we are told (pp. 35, 36), " diverge 

 from the mouth to the tips of the rays, following the ventral furrows 

 of arms and pinnules. When subtegminal, they enter the calyx by 

 means of the ambulacral or arm, openings at the upper edge of 

 the dorsal cup ; when tegminal, they follow the surface of the disk. 

 They contain the food-groove, the ambulacral vessels, the ovarian 

 tube, and the axial canal. The food-groove forms the upper passage. 



^ First proposed in F. A. Bather, "Wachsmuth and Springer's Classification, 

 etc." : Natural Science, sii, p. 341, May, 1898. 



2 P. H. Carpenter, " 'Challenger' Eep. Stalked Crinoids," p. 76, 1884. 



