TRENTON LIMESTONE. ', 87 



Genus ECHINO-ENCRINITES. 



Echino-encrinite}, Herman Von Meyer, 1826. Karstner, Arcliiv. fur die Naturlelire, Vol. vii. p. 1S5 - 



19-2, pi. 2, fig. 1 - 5 ; Vol. viii. p. 232 - 237. 

 Echinosplueritcs, Pander, 1830, Sp. Bronn, 1835, Sp. 

 Goniocrinittn, Eichwald, 18-10. 



Echino-encrinus, Volborth, 1842. > 



Sycocystites, Von Buch, ISM. 



This genus is one among the few which Von Ruch has incliuicil in his family Cystidea, 

 a group intermediate between the Echinidea and the true Crinoidea, and whicii pass into 

 the latter by the genus Caryocrinus, wiiich combines in some degree the characters of 

 both groups. 



The discovery of a species of this genus among the fossils of our older strata furnishes 

 another interesting link, connecting in their palaeozoic characters the rocks of the European 

 continent with those of America, and showing that at so early a period, when the peculiar 

 forms of Echinodkrmata, the Crinoidea, flourished in considerable numher.s, a genu.s also 

 existed which indicated a structure intermediate between that then numerous family, and 

 the future Echinidea, a portion of this great group being at the same geological period 

 represented by a true Asterias. 



The following extract, translated from the observations upon this genus in the second 

 volume of the Geology of Russia and the Ural Mountains, will convey a more definite idea 

 than my own language ; since, thus far, I have had no opportunity of examining anj' other 

 than very imperfect specimens. 



This easily characterized genus belongs, as well as the Echinospii>erites, to the Crinoidea with 

 closed summits and destitute of arms, or the Cystidea of M. de Bucii ; but it is distiaguished from the 

 first, by the small number of its plates, their form and their regular arrangement. We find in them, 

 indeed, only four basal plates, ten intermediate plates forming two ranges of five each, and five superior 

 plates which imite at the summit. Of the four basal plates, three are quadrangular, and the fourth becomes 

 pentagonal by the truncation of its salient angle. This last is exactly opposite to the two poriferous 

 rhombic plates, of which we shall speak immediately ; and upon its truncated side is placed one of the 

 plates which extends to the great lateral circular aperture, and which helps to form its contour. This 

 opening is free, without enclosing plates ; and as this is the only one, except the mouth, which we discover 

 on the surface of these bodies, it is very probable that it served both as the anus and as an ovarian 

 aperture. M. Volborth supposes that it was divided in the interior, to serve this double function. It is 

 certain that we see on none of our specimens the convex and pentagonal star, which is always remarked 

 on the Echinosphaerites. 



Another very important character of the Echino-encrinites, is their being provided with a thick, 

 round, creuse, elastic and contractile stem, which, by its thickness, contrasts with the small, and still so 

 little known stem, of the other genera of the group Cystidea. This stem is not articulated like those of 

 the Encrinites, and appears to be composed of tubes resting one within the other, and graduated like the 

 compartments of a spyglass : it is besides covered with longitudinal strias, and appears to u.s, as also to 

 M. Volborth, very analogous to, if not identical with, the Comvlites serpularius of authors.' 



• See fig. 3, p. by. 



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