1854.] 



NEW GENERA AND SPECIES OF CYSTIDEA. 



273 



The grooves for the reception of the brachial appendages in the 

 Cystidem are shallow excavations in the surface of the regular 

 plates of the body, and in Glyptocystites midtipora, when the 

 arms are removed, it would not be suspected from any indication 

 remaining after the specimen has been slightly worn that the)' had 

 ever existed. In this fossil, however, the radial furrows, supposed 

 to be the grooves for arms, are formed of an arrangement of special 

 plates, which constitute at the same time a part of the general 

 covering of the body. 



True arms have an ambulacral and an antambulacral side.* 

 If the latter were placed downwards, resting on the bottom of the 

 grooves, as is the position of the arms in the genera Pseudocri- 

 nites, Glyptocystites and others, then it would close all those pores 

 in the rays, and they would be useless. But if, on the other hand, 

 the ambulacral side of the arm be placed downwards, then all its 

 own pores, if any, would either be closed or else open only into 

 the interior of the body through the apertures of the grooves be- 

 neath. 



Neither do those apertures in the rays appear to have been the 

 openings of alimentary canals for the nourishment of rows of 

 tentacula placed on the rays, like the tentacula which fringe the 

 borders of the pseudambulacral-fields of the Pehtremites. Their 

 great size seems to preclude this idea, and again on the under side 

 of the ray there are no traces of that peculiar tubular or reed-like 

 apparatus {Rohren Apparate), described by Koemer as existing 

 beneath the pseudambulacra.f 



Each ray terminates at the mouth in a single plate, which 

 forms one side of the mouth. When viewed from the under side 

 these five terminal plates are seen to be pentagonal, and touch 

 each other, as seen in Fig. 11: But on the upper side the sutures 

 between them are concealed beneath five other plates placed upon 

 them, and which form live elevated corners at the angles of the 

 mouth. The pores which, in the rays beyond those plates, make 

 their way between the joints, here seem to penetrate through the 

 margins of the upper terminal plates, and one exactly over the 

 corner of the mouth is larger than the others. In the body of 

 the rays the pores can be clearly seen on the underside, but I can- 

 not ascertain whether those on the upper series of the ten oral 

 plates penetrate to the interior or not. 



When these new characters are compared with those of Agela- 

 crinites, the fossil certainly seems to constitute a different genus. 

 Professor Hall defines the genus Hemicystites as follows : — 



" Body circular, depressed at the margins, centre elevated, com- 

 posed of an unequal number of imbricating plates ; arms five, ad- 

 hering, radiating from the centre, and composed of a double series 

 of alternating joints ; an ovarian orifice closed by triangular plates; 

 an oral and an anal orifice, with a porous tubercle near the apex." 

 Pal. N. Y. Vol. 2, page 245. He afterwards says in a note at 

 page 355 of the. same work, "This genus is apparently identical 

 with Agelacrinites of ■ Vanxtxem, the description and figure of 

 which I had overlooked at the time this volume was written." 



If we take the above description of the genus Hemicystites as 

 a definition of Agelacrinites, then the fossil now under considera- 

 tion cannot readily be determined to be a species of the latter 



* "Arms are free radii w th an ambulacral and antambulacral 

 side." J. JIuller. On the Structure of the Echinoderms. Annals of 

 Natural History, January, 1854, page 8. 



f See Roemer. Monographic der Fossilen Crinoiden familie der 

 Blastoideen und der Gattung Pentatrematites im besondern ; page 19, 

 Taf. I,, 2, 6. 



genus. The difference in the position of the mouth in the two is 

 quite sufficient to separate them. In our specimen, the rays pro- 

 ceed as it were out of the mouth, whereas in Agelacrinites the 

 mouth is situated on one side of the apex in one of the spaces 

 between two of the rays. 



It may be that Agelacrinites is the young of this species. 

 About six years ago, I found a fossil almost exactly like that 

 figured by Vanuxem, and last summer on the same spot a frag- 

 ment of one of the rays of a specimen of this large kind. In the 

 fall of 1852, I discovered another, also like Vanuxem's fossil, on a 

 stratum of limestone, which projected from beneath another, and 

 last spring, on returning to the place and removing the upper 

 layer, and about three inches of shale, the seven specimens above 

 mentioned were disclosed, with a prodigious number of fossils of 

 other species. 



Neither of the small specimens are in my possession, but judg- 

 ing from Vanuxem's figure and Professor Hall's description of 

 Hemicystites, and also from recollection of the structure of the 

 fossils, I have no doubt but that they are Agelacrinites. If so, 

 then the circumstance of their having been found in two instances 

 in association with the larger organisms, points to the conclusion 

 that they are the young of the latter. Agelacrinites may there- 

 fore be, as Professor Hall has suggested, " the embryonic condi- 

 tion of a higher organization." 



If we regard these two forms found here as distinct species of 

 Cystidea, then there are certainly twelve species of this extinct 

 order imbedded in the Trenton limestone in this locality, for be- 

 sides those described in these two papers, there are the fragments 

 of two others. One of these I have often met with in detached 

 plates, containing half of a pectinated rhomb, and of the other I 

 have a fragment of one side, consisting of about twenty plates. 

 That they are parts of Cystideans there can be no doubt. 



There are also several specimens of Pleurocystites, which appear 

 to be different from those described in the first paper. 



These new fossils were all discovered in the upper one hundred 

 feet of the Trenton limestone, associated with between twenty-five 

 and thirty new species of Crinoids, some of them beautiful forms. 

 They belong principally to the genera Heterocrinns, Glypto- 

 crinus, Ilomocrinus, Lecanocrinus, Thysanocrinus, and two 

 or three new genera. The heads are mostly crushed, but suffi- 

 ciently perfect to make out the form and arrangement of plates. 

 It will be no doubt useful to those examining the rocks of the 

 Ottawa, to know that nearly all the smooth round columns of 

 Crinoidea, so abundant, may be referred to two fine species of 

 Thysanocrinus. This encrinite has a branching root and a 

 round, smooth, straight column, which, for a few inches below 

 the head, becomes anuulated by alternately larger and smaller 

 joints, as shown in the fragment of the stem seen attached to the 

 figure of T. Liliformis, in the 2d volume of the Palaeontology of 

 New York, Plate 42. 



Nearly all the large moniliform columns are those of several 

 magnificent species of Glyptocrinus, of which I have the heads. 

 1 believe that the discovery of two species of Lecanocrinus is the 

 first appearance in our strata of Crinoids, with three plates only 

 in the pelvis, so low down in the series as the Trenton limestone. 

 These I found during the month of November last. 



The Cystidea described in these two papers, although different 

 even in genus, when viewed altogether as a group, resemble those 



