18 85.] NATUBAL SCIENCES OF PHILADELPHIA. 273 



the condition of the Pentacrinoid larva, as suggested by Car- 

 penter, it should have its anal opening beneath the orals, and not 

 pierced through the upper portion of one of them. The very 

 fact that the anal structures are invariably connected with the 

 proximals, proves to us that the latter are interradials, developed 

 around the left peritoneal tube, in a similar manner as the cabyx 

 interradials around the right, and that, as such, they are homol- 

 ogous with the first interradial plate in the cabyx, and not with 

 the basals, as suggested by Carpenter. The interradials, and not 

 the basals, enclose the anal plates ; there is not a single instance 

 known to us in which an anal plate enters the basal ring. The 

 az} y gous side of the proximals is generally composed of three 

 adjacent pieces transversely arranged, and a divided interradial, 

 which encloses an anal plate, as in the case of the primary calyx 

 interradials. Sometimes, however, the anal plate is lifted out, 

 and the first row is occupied exclusively by a bisected proximal 

 (PI. 7, figs. 8-10), as in the apical system of Actinocrinas. 



It has been observed by Goette (Vergleichende Entwickelungs- 

 geschichte d. Comatula mediterranean, Arch. f. Microsk. Anat., 

 1876, Bd. xii, pp. 621-624), that there exists a complete homology 

 between basals and orals, and that both were developed spirally, 

 the former round the right, the other round the left peritoneal 

 tube. Upon these important observations, with which we fully 

 agree, Carpenter undertakes to build up his proof that the proxi- 

 mals are the orals of the Palaeocrinoidea. He reasons as follows 

 (Chall. Rep., pp. 169, 170) : " The basals are primitively next to 

 the abactinal centre in Urchins and Stellerids, and are only re- 

 moved from it in the Crinoid by the growing stem ; while the 

 orals are next the actinal centre, no plate being developed there, 

 however, in the recent Crinoid. Did it appear, it would only be 

 in the way, and have to undergo resorption to a greater or less 

 extent, just as the dorsocentral of many Urchins is more or less 

 completely resorbed after the appearance of the anus." 



The discovery of a dorsocentral plate in the larva of the Urchins, 

 Starfishes and Ophiurids b}- Carpenter, Sladen and Liitken, which 

 Carpenter thinks is represented by the terminal plate at the base 

 of the larval stem in Comatula, is to our minds no proof, in the 

 total absence of embrj'ological evidence, that there was a similar 

 plate at the oral side. The so-called " orocentral " is said to be 

 present exclusively in Palseocrinoids, but there it is found in all 

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