TROOST *S CRINOIDS OP TENNESSEE — E. WOOD. 103 



Interscapulars [interbrachials] five, pentagonal placed in the angles formed by the 

 heptagonal plates of the second costals [radials], and support three small tumous plates 

 between the arms upon which rest the coronal integument [tegmen]. 



Arms, five — subdivision unknown. 



Observations. — The name Balanocrinus was preoccupied, having 

 been used by Louis Agassiz in 1845 for a genus of the family Pen- 

 tacrinidir. Full descriptions of this genus, references to which are 

 to be found in the synonymy, have been given by Roemer, Wachs- 

 muth and Springer, and others. 



LAMPTEROCRINUS TENNESSEENSIS Roemer. 

 Plate 7, figs. 8, 9, 10. 



Balanocrinites sculptus Troost, Proc. Amer. Ass. Adv. Sci., II (read 1849), 1850, 

 p. 60 (nomen nudum), MSS., 1850. 



Lam pterocrinus tennesseensis Roemer, Die Sil. Fauna des westl. Tennessee, 1860, 

 p. 37, pi. iv, figs. la-d. — Shumard, Trans. Acad. Sci. St. Louis, II, No. 2, 

 1866, p. 379 (catalogue name). — Wachsmuth and Springer, Rev. Palseo- 

 crinoidea, II, 1881, p. 201 (catalogue name). — Miller, North Amer. Geol. 

 and Pal., p. 257 (catalogue name). — Wachsmuth and Springer, North Amer. 

 Crinoidea Camarata, 1897, p. 208, pi. xm, figs. 10 a-d. 



The following description is by Troost: 



It resembles the acorn of the oak particularly if we consider it without the column. 

 It has apparently a cylindrical form but when we take a top or bottom view it is pentag- 

 onal. It is beautifully and regularly ornamented with elevated ridges, proceeding 

 from the angles of the pentagonal column and ascending to the centres of the costals 

 [basals]. From five to six of these ridges join together in the centre of the first series 

 of costals [basals]; on the second series, (heptagonal plates) we have from six to seven, 

 on the scapulars [first primibrachs] we have only three which join together immedi- 

 ately below the arm joints, while on the interscapulars [interbrachials] we have again 

 from five to six ridges forming in this manner by their junction a number of acute and 

 obtuse triangles and ornamenting the whole surface most elegantly, and which will 

 be better conceived by examining the figures than can be conveyed by words. In 

 these delineations I have endeavored to represent the different sides of the fossil 

 which show any variation in the configuration produced by the irregularity in the 

 number of these ridges on the various plates, which arrangement on the whole exhibits 

 such remarkable regularity. In most of them these ridges are single as represented 

 in the figures, in others, without exhibiting a specific difference, they are double and 

 triple, and in this case the joints of the plates are obliterated. 



They occur in Decatur County, Tennessee, where they are pretty abundant, never- 

 theless perfect specimens are rarely met with — they are mostly changed into silex. 



Observations. — Doctor Troost failed to recognize the existence of 

 more than one primibrach in the radial series, hence his figures are 

 incorrect in the upper portion of the calyx. 



The full description of the species by Roemer did not appear until 

 ten years after Troost's description and figures were ready for pub- 

 lication, but as the former is the first to be published the species 

 is lost to Troost. 



Formation and locality. — Brownsport limestone, Eucalyptocrinus 

 zone of the Beech River formation. Decatur and Wayne counties, 

 Tennessee. 



Cat, No. .39920, U.S.N.M. 



