28 Dr. P. H. Carpenter on the 



student ; but they are both alike marked " a, parties decal- 

 cifi(5cs du squelette." 



We have seen tliat in tlie explanation of fig. 268 two of 

 the first radials are described as " pieces constituant le sommet 

 du calice ; " and on p. 529 we read " les cinq premiers 

 radiaux qui fornient le sommet du calice," &c. But on the 

 page immediately preceding (528) we are told that '' ce som- 

 met est occup(5 par un seul pi^ce pentagonale, la plaque 

 centra- dor sale ^'' a description which is scarcely consistent with 

 the explanation of fig. 268 ; while we also read tliat the first 

 radials are " fusionndes avec la plaque," although the fibres 

 effecting this fusion are described in the explanation of fig. 276 

 as the muscles between first and second radials ! Various 

 descriptions are also given of the mode in which the first 

 radials are united laterally to one another. The explanation 

 of fig. 264 runs thus : — " a, pieces calcaires du sommet, 

 sdpar^jes par des faces articulees, &, dans lesquelles s'enga- 

 gent les muscles transversaux c, internes ; 6?, muscles se 

 rendant aux bras naissants." But on the next page the 

 same parts are described as follows : — " Les pieces calcaires 

 (a) du sommet du calice sont rdunies par de fortes masses 

 musculaires id) et par des sutures lineaires (J) traversees 

 cgalcment par des muscles (c)." Thus then the extensor 

 fibres (c/), which on one page are spoken of as uniting the 

 arms to the " sommet," are described on the next as joining 

 together the calcareous pieces of the "sommet;" and this 

 same " sommet " is said on p. 528 to be occupied by only one 

 pentagonal piece, the centro-dorsal ! 



The authors admit that the section represented in fig. 264 

 passes " un pen obliquement sur la plaque centro-dorsale." 

 Had it been really horizontal they would have seen nothing 

 of the three " faces articulees " (/>), which are described on 

 the next page as linear sutures between the first radials ; 

 while on p. 529 we are told that these same first radials are 

 " fusionnes ensemble," and nothing whatever is said about 

 the " muscles transversaux internes," which are marked (c) 

 in fig. 264 and described on p. 530 as " puissantes masses 

 musculaires " ! Do the authors really believe that the first 

 radials were united to the centro-dorsal and to one another by 

 muscles, and that these portions of the calyx were movable 

 on one another? The fibres which eflfect this union are alto- 

 gether of a different nature from those forming the great 

 muscular bundles which are attached in the fossai at the 

 ventral ends of the articular faces of the first radials and of 

 the arm-joints (c of fig. 268,/ of figs. 279 and 280). These 

 have the usual histological characters of the muscles in other 



