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PROCEEDINGS OF THE ACADEMY OF 



tweeu two of the produced rays of the vault, which we have termed pseudo- 

 bracliial appendages, or false arms. In clearing away the matrix of this 

 specimen, we had cut just far enough to expose the edges of the arms on each 

 side of the deep ambulacral furrow, so that each of these edges presents the 

 appearance of being a separate and distinct, very slender arm, composed of a 

 single series of pieces, and without any ambulacral furrow on the outer or 

 ventral side ; whereas there is a well-defined ambulacral furrow, bearing the 

 tentacula along its margins, on the outer side of the arms, and when the matrix 

 is removed from these ambulacral furrows, the arms can be seen to be composed 

 each of a double series of small alternately-arranged pieces. It is barely possi- 

 ble that in specimens of this species with the arras perfectly preserved, that the 

 ambulacral furrows may be covered on the outer or ventral side by a double 

 series of alternating pieces, and that the tentacula* may connect with little 

 openings along each side, though there certainly appear to be only open fur- 

 rows in the specimens examined. 



It is worthy of note, in this connection, that there certainly are species, 

 agreeing exactly in all other known characters with this genus, that have no 

 open furrow along the outer or ventral side of the arms, which are distinctly 

 seen to be round on the outer side, and show there a double series of interlock- 

 ing pieces along their entire length, while the tentacula connect along the 

 inner, or under side, as the arms are seen hanging down. This is clearly seen 

 to be the case in a beautiful specimen of G typus {=Trematocrinus typus, Hall) 

 in Mr. Wachsmuth's collection, and we can scarcely doubt that in this species 

 there is an open furrow on the inner (under) or dorsal side of the arms. If 

 not, the arms must be tubular, in consequence of having the ambulacral canal 

 aclosed all around, excepting at the points where the tentacula connect along 

 each side. 



3. Cyaihocrinus, Miller. Specimens of this genus showing the vault (more 

 properly the ventral disc) have very rarely been seen. In England a few ex- 

 amples have been found, and these have been supposed to show two openings, 

 one central and another lateral ; the latter, according to Prof. Philipps' and 

 Mr. Austin's figures, being provided with a slender marginal tube, or so-called 

 proboscis. Some of Mr. Wachsmuth's specimens, however, of C. malvaceus and 

 C. loiuensis, Hall, showing the vault, have led us to doubt the existence of a 

 central opening in the vault of this genus, when the specimens have this part 

 entire. The specimen of C. malvaceus shows the remains of the usual narrow 

 lateral proboscis, and also has an opening in the middle of the vault, but from 

 the appearance of this opening, as well as from the structure of the vault of a 

 specimen of C. lowensis, in which this opening is closed, we can scarcely doubt 

 that it was also closed in the specimen of C. 7nalvaceus, when entire. The re- 

 maining parts of the vault of the C. ynalvaceus mentioned consist of only five 

 comparatively large pieces, alternating with the upper inner edges of the first 

 radial pieces, — the one on the anal side being larger than the others, and form- 

 ing the base of the inner side of the proboscis. These five pieces connect wilh 

 each other laterally, and extend inward some distance, bat not so for as to 

 meet at the centre, where there is a subsemicircular opening, nearly as large 

 as that in the remaining base of the proboscis. Along each of the sutures 

 between the five vault pieces mentioned, a comparatively large furrow extends 

 inward from each arm-base to the central opening. These we regard as con- 

 tinuations of the ambulacral furrows from the arms, though there is also a mi- 

 nute opening at each arm base, passing directly downward into the cavity of 

 the body, which was probably for the passage of the arm-muscles. 



Looking at this specimen alone, one would naturally suppose there must 



* We use the term tentacula here in the sense it is generally used by paljeontologists, 

 with reference to the delicate pinnulre along the arms of Crinoids, and of course not as 

 applying to the minute flestiy organs along the ambulacral furrows, usually termed tenta- 

 cles by those who have investigated the recent Crinoids. 



[Dec. 



