166 PROCEEDINGS OF THE ACADEMY OF 



Locality and position. The only specimen of this fossil we have seen is in a 

 granular mass of decomposing chert, containing some fragments of small cri- 

 noid columns. It was obtained from the Subcarboniferous rocks of Missouri, 

 but the exact locality and position we have been unable to ascertain. 



Note on the genus GILBERTSOCRINUS, Phillips. 



BY F. B. MEEK. 



Genus GILBERTSOCRINUS, Phillips, 1836. 

 Gilbertsocrinus, Phillips, Geol. Yorkshire, part ii., p. 207, 1836. 

 Goniasteroidocrinus, Lyon and Casseday, Am. Jour. Sci. xxviii. p. 233, 1859. 

 Trematocrinus, Hall, Sup. Iowa Report, p. 10, 1860. 

 Phillips' diagnosis of this genus reads as follows : 



" Basal joints five, forming a pentagon ; suprabasal [subradials] five, hexa- 

 gonal, forming a decagon with five re-entering angles, from which proceed 

 five heptagonal first costals [first radials] and five hexagonal second costals, 

 [second radials], bearing a pentagonal scapula [third radial] supporting joints 

 [secondary radials] which combine into rounded arms perforated in the centre. 

 First in.tercostals [first interradials] pentagonal. The following species have 

 been usually referred to Rhodocrinus, Miller, from which, it appears to me, they 

 differ entirely." (Phillips.) 



He mentions but the following three species, viz., G. calcaratus, G. mammil- 

 laris and G. bursa, all from the subcarboniferous. His specific descriptions are 

 very brief and unsatisfactory, but his figures are tolerably good, and give a 

 , sufficiently intelligible idea of the generic characters of the group. From these 

 .figures, and his description, it is therefore evident that the formula, in accord- 

 ance with the later improved nomenclature, may be stated as follows: 



Generic formula of Gilbertsocrinus. 



Basal pieces 5. 



Subradials 5. 



Radials 3x5. 



Secondary or supraradials 3 or 4x10. 



Anal and interradial pieces 12 to 15x5. 



Pseudo-brachial appendages (arms of some authors) 5, located over the rays. 



Arm-openings (ambulacral,) 10, located directly under the pseudo-brachial 

 appendages. 



On comparing this formula with the following, given by Messrs. Lyon and 

 Casseday, of Goniasteroidocrinus, cited above, the close relations of these crinoids 

 will be, apparent. 



Generic formula of Goniasteroidocrinus. 



Basal pieces 1x5, pentagonal, perforation not visible. 



Subradial pieces 5, hexagonal, nearly equal in size. 



Primary radial pieces 3x5, first spiniferous. 



Secondary radials 3X 10, hexagonal. 



Interradial fields [including the anal area] 5x13 to 14, [pieces each]. 



Interbrachial fields 5x1 to 9, [pieces each]. 



It may be proper to explain that the term pseudo-brachial appendages 

 is used in the formula of Gilbertsocrinus, for the parts regarded by Phillips and 

 by Messrs. Lyon and Casseday as arms, and that arm-openings, not alluded 

 to by Phillips in his description, though clearly shown in his figur. s, are men- 

 tioned. These openings were not observed by Lyon and Casseday, because 

 they were hidden in their specimens by the attachment of the small pendulous 

 true arms, or, in the absence of the latter, by portions of the matrix, as is 

 known to the writer from the examination of specimens of their typical species 

 loaned by Mr. Lyon. 



/ [Aug. 



