i 



new Species of Crinoids. 161 



Prof. Williams does not refer to the stem of the generic type 

 eyond giving its thickness ; but the small portion of it shown 

 in his fig. 1, in close proximity to the body of the crinoid, 

 resembles the stem of H. Carpenter i in consisting of alterna- 

 ting larger and smaller joints ; and it is very probable that 

 nodes with cirri were also present, as in this latter species. 

 The other fragments figured by him as portions of the stem 

 (figs. 7 and 8) are so entirely different in the thickness of the 

 stem itself and of the individual joints, as also in their smooth 

 and uniform characters, that in the absence of confirmatory 

 evidence one cannot regard them as belonging to the same 

 species. 



Apart from the possession of articulating spines the relations 

 of HystricrinitS) as already noted by Williams*, are very 

 close to Hexacrinus, Austin f, a genus of crinoids which, 

 according to Wachsmuth and Springer J, is almost exclusively 

 limited to the Devonian formation in Europe, only fragments 

 of a single species having been discovered in America. The 

 number and arrangement of the basals, the first radials, and 

 the anal plate are very similar in the two genera ; but a com- 

 parison of the other features is rendered difficult on account of 

 the uncertainty which prevails as to the definite characters of 

 Hexacrinus. According to Zittel § this genus resembles 

 Platycrinus in having a single axillary above the first radial, 

 although rarely another intermediate so-called radial is present, 

 and interradials are wanting. Wachsmuth and Springer ||, 

 on the other hand, state that there is one axillary above the 

 first radial, that the anal plate supports two or three plates, 

 and that the interradial series is composed of a single large 

 plate which rests within a notch between two radials. An 

 examination of the characters of Heocacrinus inter scapularis, 

 Phill. sp. ^j, the type of the genus, does not avail conclusively 

 to solve the question, for unfortunately the number of radials 

 above the first is not shown in Phillips's and Austin's figures ; 

 the arms and stem are wanting, but there are two zones, of 

 two plates each, in the anal interradial area, and of three 

 plates each in the other interbrachial or interradial areas, so 

 that in this last feature the typical example of the genus 

 differs from both Zittel's and Wachsmuth and Springer's 



* Op. cit. p. 82. 



t Mon. Rec. and Foss. Crinoids, 1843, p. 252. 



t " Revision of the Palseocrinoidea,'* part ii., ' Proceeding's of the 

 Academy of Natural Sciences of Philadelphia,' 1881, p. 253. 

 § Handb. dor Pal. vol. i. p. 305. 

 || " Revision," ii. p. 253. 

 ^1 Pal. Foss. Cornw., Geol. Suit. Mem. 1841, p. 28, pi. xiv. tig. 39. 



