84 PEOCEEDINGS OF THE ACADEMY OF 



Dr. F. Roemer, who ia 1852 published a beautiful and valuable monograph of 

 most of the species of this group then known, giving accurate illustrations of al- 

 most the entire anatomy of the genus Pentremites, including the arms or pin- 

 nulae, and other parts not previously illustrated, regarded the summit openings 

 in that genus as stated above. He noticed, however, that in Nucleorinus 

 (= E/iccrinus, Roemer) the central opening is covered in by a series of small 

 plates, and that in Cadaster, the openings corresponding to the so-called ovarian 

 apertures of I'entremites seem to be absent.* At that time Dr. R. was appa- 

 rently not aware of the fact that Owen and Shumard had, in 1850, announced 

 that all of the summit openings in Pentremites Godoni are, in perfect specimens, 

 covered by minute plates, f as had been shown by himself to be the case with 

 the central opening in Nudeocrinus, since he seems to have regarded this char- 

 acter as one of the distinctions between the latter genus and Pentremites. 



Dr. Shumard has also since shown that this character not only occurs in 

 other true Pentremites, such as P. conoideus, P. sulcatus,X etc., but that at least 

 the central hiatus in several species of the genus Granatocrinus (= Pentremites, 

 section Elliptici, of Roemer), such as G. Sai/i, G melo and G. Nortvoodii, is also 

 known to be covered in the same way, in perfectly preserved specimens. 



Dr. C. A. White, the present able State Geologist of Iowa, also announced, 

 in a very interesting paper on the summit structure of the Blastoidea, pub- 

 lished in 1863, that in well preserved specimens of Pentremites steUiformis the 

 central and anal openings are both covered by small pieces^ He likewise 

 stated in the same paper that he had seen si)eciuiens of Granatocrinus JVor- 

 u'oociii with the central hiatus covered by small pieces, and that from this cov- 

 ering a double series of minute alternating pieces could be seen extending out 

 the mesial furrow of each pseudo-ambulacral area for some distance. || 



We have also seen specimens of Pentremites steUiformis, Granatocrinus melo, G. 

 Korwoodii and G. Sayi (most of them belonging to Mr. Wachsmuth's collection), 

 showing the central opening covered by small pieces, and continuing out from 



and the other two, one on each side of this, like those of other lateral openings, are most 

 generally viewed as ovarian apertures. In some species of Granatocrinus, however, the 

 ■openings corresponding to the four in /'>jtirf?;i*'«, divided into two each witliin, actually 

 appear at the surface as four pairs of distinct openings ; while in other types, such as i\'«- 

 choriiius, and some species apparently allied to Chdastcr (more properly Codonaster), the 

 supposed ovarian apertures appear as five pairs of separate openings, all distinct from 

 each other, as well as from the anal opening. 



As was first illustrated by Dr. Roemer, tliese so-called ovarian pores are known to con- 

 nect with a series of compressed tubes within the cavity of the body, extending down 

 along the inner side of each pseudo-ambulacrum so as to connect with the numerous 

 minute pores passing through the lateral margins of these areas. Of these tubes we have 

 ascertained tliat, in Granalncrinus melo, G. Norwoodii, and a new species described in this 

 paper (which are all of this genus in which we have seen them), there are two pairs to 

 each pseudo-ambulacral area ; while in Ptntremiies Godoni, P. pyriformis and P. liheinwardiii 

 there seem to be eight tubes to each field, and in the so-called Pentremites steUiformis 

 twelve to each field. We are therefore inclined to think thenumber of these tubes may be 

 found constant, or nearly so, in each genus, since the area occupied by the twelve tubes in 

 I'enliemiies steUiformis is not so wide as that occupied by eight in some i^e^itremt^es proper. 



* We have not had an opportunity, recently, to examine good specimens of any of the 

 typical forms of Cudaster, but it has frequently occurred to us that possibly the deep linear 

 furrows seen on the upper surface of these fossils, running parallel to the pseudo-ambu- 

 lacra, and which Prof. McCoy and others seem to have supposed to be punctured at the 

 inner ends, may connect, by these punctures, with the tubes within, and thus represent 

 the so-called ovarian openings in the other Blastoids. The fact that these openings cer- 

 tainly are represented in Pentremites stdltfurmis of Owen and Shumard, by linear slits, 

 seems to favor this conclusion. But as there is only a single one of these slits on each side 

 of each of the pseudo-ambulacra in the last-mentioned type, instead of four to six, and 

 they exist in the anal, as well as the inter-ambulacral areas, it is evident that tliese and 

 other differences are of sufficient importance to warrant the separation of this species 

 from Cadaster, to which it has sometimes been referred. And as it differs from Pentremites, 

 in having the so-called ovarian pores represented by ten distinct slit-like openings, and in 

 other characters, we would propose to establish for its reception a new genus, witli the 

 name Codonites. 



t Jour. Acad. Nat. Sci. Philad. vol ii (quarto series), p. G5. 



t Trans. St. Louis Acad. Sci. vol. i, p. 243, pi. 9, fig. i, 1858. 



g Jour. Boston Soc. N. H. vol. vii, p. 482, va&i. 



II Missouri Geol. Report, p. 18G, 1855. 



[April, 



