TROOST'S CRINOIDS OF TENNESSEE E. WOOD. 97 



judging from fragments <>f this pelvis in my collection no suture is visible, and only 

 a very small cavity in its interior, and no traces of any canal towards the base being 

 perceptible — in fact almost the whole pelvis is solid carbonate of lime. 



All the plates are very thick. The articulating surfaces broad and transversely 

 irregularly striated, and possess a small abdominal cavity. 



It occurs near Huntsville, Alabama, in Carboniferous strata, and I found numerous 

 fragments of it in the Silurian in Decatur County in Tennessee, so that it seems to 

 belong to two geological ages. 



Observations. — The infrabasals of Doctor Troost's type are not pre- 

 served, but his collection contains the infrabasals of a slightly larger 

 individual used for the description. The transverse, irregular striae, 

 mentioned by Doctor Troost, on the upper surface of these plates are, 

 no doubt, the ramifying furrows described by Wachsmuth and 

 Springer [1886, p. 263]. 



Formation and locality. — Kaskaskia limestone. Huntsville, Ala- 

 bama; Chester, Illinois; Washington County, Arkansas; Crittenden 

 County, Kentucky. 



The fragments reported by Doctor Troost as from Decatur County, 

 Tennessee, are probably incorrectly identified, as his collections at 

 that locality are from the Brownsport limestone and it is unlikely that 

 the species persists from that horizon to the Kaskaskia. 



Cat. No. 39918 U.S.N.M. 



AGASSIZOCRINUS, species undetermined. 



Plate 7, figs. 6, 7. 



Agassizocrinites Troost, MSS., 1850. 



The description by Troost is as follows: 



1 possess numerous basal or pelvic parts of the Agassizocrinites which I think 

 belong to other species. Some have the form as represented by fig. 2, plate 7, in 

 which the joints are well preserved, in some of them the junctions are entirely obliter- 

 ated. Others have the form of a segment of a sphere — in these no divisions are per- 

 ceptible, and they probably belong to different species. They occur in different 

 formations — I found some near White's Creek Springs — Carboniferous — others near 

 Huntsville, Alabama, also Carboniferous, while the greatest number were found in 

 Decatur County, Tennessee — Silurian. 



Observations. — Of the fragments mentioned above only the one 

 figured is to be regarded as possibly of an undescribed species. The 

 specimen from which the figure is drawn is missing from the collec- 

 tion, but if the drawing is accurate it differs from Agassizocrinus 

 dactyliformis in the shorter infrabasals and radials and consequently 

 in the much shorter and broader calyx. 



The locality of the figured specimen is not designated. Its horizon 

 is probably Upper Mississippic or Carbonic as the genus is not known 

 to have a wider range. 



The fragments from Decatur County may belong to different 

 species or even to different genera but in the absence of either descrip- 

 tions or figures it is impossible to determine their character. 

 63330—09 7 



