THOOST'S CRINOIDS OF TENNESSEE E. WOOD. 



79 



PERIECHOCRINUS (?), species undetermined. 



Plate 6, figs. 6, 7. 



Actinocrinus moniliformis J. S. Miller, Nat. Hist. Crinoidea, 1821, p. 115. — 

 Phillips in Murchison's Sil. Syst., 1839, p. 673, pi. xvm, fig. 4. 



Actinocrinites moniliformis (?) Troost, Proc. Amer. Ass. Adv. Sci., II (read 1849), 

 1850, p. 60 (nomen nudum). . 



Periechocrinus moniliformis Wachsmuth and Springer, Rev. Palseocrinoidea, 

 II, 1881, pp. 128, 132. 



The original description by Troost is as follows: 



The superior part. The fingers — forty in number. 



Our fossil resembles the superior part, the fingers of the figure given by Phillips of 

 the Actinocrinites moniliformis (Murches. Sil. Sys. pi. 18, fig. 4). This species was 

 conjectured by Miller and described by Phillips. It is only a conjecture of mine 

 whether the Tennessee fossil really belongs to this species. It can not be decided, as 

 the whole of the cup is wanting. If we take the number of ringers only into consid- 

 eration, then it may also belong to the A. polydactilus of Miller, which according to 

 this author may have 30 or 40 ringers. According to Phillips the A. moniliformis has 

 40 fingers and our specimen also has 40 fingers. A circumstance mentioned by Miller 

 on the authority of Lhwyd is the extraordinary length of the proboscis of the A. 

 polydactilus, which would favour placing it in the species of the A. polydactilus. In 

 our specimen the proboscis may be seen in fig. [7] and about 1^ inch above it where 

 the specimen is injured, the proboscis continues, — in fact I have fragments of pro- 

 bosces which are 3 inches long and which I consider as belonging to similar crinoids as 

 our specimen. It is therefore undecided whether our fossil belongs to A. moniliformis, 

 A. polydactilus, or whether to a new genus. I have nevertheless thought proper to 

 rank it provisionally as A. moniliformis, because it resembles more the fingers as they 

 are represented by Phillips than those that are represented by Miller of the A. poly- 

 dactilus. 



The same specimen contains a fragment of a column which is composed of joints 

 with rounded sides, but not alternating small and large; it is perforated by a large 

 pentalobed alimentary canal [lumen], striated near the margin and is 14 mil. m. in 

 diameter, consequently if this column belonged to this crinoid, it must have been of a 

 gigantic size. 



I found it on the banks of the Cumberland river near Clarksville in limestone of the 

 same geological age as that in the vicinity of Nashville (Silurian) [?]. 



Observations. — It is impossible to say to what species or even to 

 what genus these arms belong. Doctor Troost has referred them to 

 Periechocrinus moniliformis (Miller), since they resemble the arms of 

 that species in number and general appearance, but it seems probable 

 that if really of the genus Periechocrinus they belong to species 

 occurring in Tennessee. In the absence of satisfactory data they 

 can not be referred to any one of these. 



Formation and locality. — Brownsport limestone? Near Clarks- 

 ville, Montgomery County, Tennessee. 



The formation upon which the town of Clarksville rests is the 

 Upper Lithostrotion bed of SafTord, correlated by him with the St. 

 Louis limestone, but Doctor Troost' s label refers the specimen to 

 strata of the age of that near Nashville ; that is, Brownsport lime- 



