228 SMITHSONIAN INSTITUTION 



paleontologists, including Lyon, and Meek and Worthen, under the name Forbesiocrinus. 

 The type to which these species belong has always attracted the attention of collectors and 

 authors on account of its striking appearance and well marked characters, and specimens of 

 some of the species have been considered the greatest prizes in the collections. It has an even 

 greater interest in connection with the critical study of the Flexibilia, because it represents 

 the culmination of the solid anal structure characterizing its family, in contrast to that of the 

 Taxocrinidae. Its special character is that the interbrachial areas are completely filled by 

 solid plates, suturally united to adjoining rays and to each other, and passing gradually into 

 the tegmen. This is the type which De Koninck and Le Hon had in mind when they expressed 

 the belief (op. cit., p. 119) that in their genus the calyx extends beyond the origin of the 

 arms, although it is not clearly shown by their specimens, and still less indicated now by 

 mine ; — which leads to the conclusion that the Belgian species represents only an early and 

 incomplete stage of that type. 



This idea is strengthened by a consideration of the stratigraphic position of the respec- 

 tive types. The whole Tournai crinoid fauna as described by De Koninck and Le Hon and as 

 represented in my collection and that of the British Museum, and also the other invertebrate 

 faunas, 1 correlate in a general way with those of the lowest part of the American Lower Car- 

 boniferous, from and including the Lower Burlington limestone down. They bear a striking 

 resemblance to the Lower Burlington — Kinderhook — Choteau — Waverly — Knobstone faunas 

 as found and studied in Iowa, Missouri, Indiana, Ohio, Kentucky and New Mexico. While 

 the species of the two continents are for the most part different, there is a similarity in the 

 general facies, or assemblage of forms, which is striking not only for what is found, but for 

 what is absent. Not a single one of the crinoid types most characteristic of the Upper Bur- 

 lington or later formations has ever been found at Tournai ; whereas certain types, including 

 the specialized Mespilocrinus, that have never passed the Burlington are well represented at 

 the Belgian locality. No competent American paleontologist, finding such an assemblage as 

 the Tournai species of crinoids and blastoids in a locality in this country, would hesitate for 

 a moment to place it below the Upper Burlington. 



Now it is a significant fact that the American species described under Forbesiocrinus of 

 the type of F. agassizi, etc., begin in the Upper Burlington and run upwards, culminating - in 

 the Warsaw ; not a specimen positively known to belong to that type has been found in any 

 lower formation. On the other hand fragments belonging beyond all question to the same 

 type as my Tournai specimens are now known to occur in the Knobstone of Indiana and 

 Kentucky, and one finely preserved and distinct species comes from the very base of the 

 Lower Carboniferous in northern Ohio. This clearly distinctive geological position, coupled 

 with the decided morphological difference between the two forms, indicates a progression in 

 the interbrachial development of the genus analogous to what has taken place in Ta.vocrinus; 

 with the difference, however, that Forbesiocrinus begins at the base of the Lower Carbonifer- 

 ous in about the same stage in which Ta.vocrinus finishes at the close of that epoch. 



The first of the new specimens (PI. XXIII, figs. la-e) is the one referred to by 

 Wachsmuth' and Springer in a note concerning Forbesiocrinus nobilis (N. A. Crinoidea 

 Camerata, p. Jj), and on which we based the opinion that the species was identical with 

 Onychocrimis. This was upon the supposition that the rays were free above the first costal, 

 and branched from the fourth distichal in curved armlets like Onychocrimis. The last obser- 

 vation is not correct. The specimen is abnormal in the right ramus of the right posterior ray, 

 giving rise at one place to a somewhat Onychocrinus-like. cluster of branches beyond the first 

 axillary, which, with the apparent freedom of the rays, certainly produces a general appear- 

 ance much resembling the facies of that genus. But in the left ramus of that ray, and in the 

 other specimen with the arms normal in three rays (fig. 2) as well as in De Koninck and 

 Le Hon s figure 2.a, the bifurcation is almost regularly dichotomous. I corrected the above 



1 Herrick, C. L., Bull. Geol. Soc. America, vol. 2, 1S91, p. 39. 



