TAXOCRINIDAE \OJ 



Taxocrinus huntsvillae n. sp. 



Plate LIX, figs. 17-25 



A very small species of type similar to that of T. shumardianus, but dif- 

 fering in general proportions, the crown being rather wider than high, and in 

 the form of the rays which instead of being broad and rounded are narrower 

 and more elevated, sometimes tending to become angular. As usually found 

 with arms folded the average dimensions of over 50 specimens are: height of 

 crown, 13 mm. ; width at level of first IIIBr, about 13.5 mm. ; diameter of base, 

 3 mm. ; spread of calyx to first axillary, 3 to 12. 



This species occurs chiefly at a single locality near Huntsville, Alabama, where I have 

 obtained it in large numbers and good condition ; and it is from a higher horizon than 

 shumardianus, being from the Ohara member of the Ste. Genevieve formation in the earlier 

 Kaskaskia. While the differences upon which it is separated from that species are rather 

 slight, they are strikingly constant. There is a remarkable uniformity in the small size, and 

 the relatively lower and broader crown, while the tendency to angularity in the rays imparts 

 a sharpness of aspect which makes the specimens readily distinguishable. Maximum speci- 

 mens do not exceed about 15 mm. in width. The interbrachials usually touch the basals, but 

 this character is not without exceptions, a few specimens being found in which the connec- 

 tion is wanting in one or more interrays. In the latter condition this form persisted spar- 

 ingly into the higher Kaskaskia beds (PI. LIX, figs. 23-25). The species is in fact an 

 intermediate stage in a little line of retrogression which marked the concluding phases of 

 the genus in the last three members of the Carboniferous — depauperate species of the short 

 type, in which the arms were growing shorter : In T. giddingei of the Warsaw, with 3 IIBr 

 like the antecedent T. ungula, the third arm division also began occasionally to have 3 plates ; 

 in T. shumardianus of the St. Louis this character became constant for the inner ramus and 

 continued to the Lower Kaskaskia in the present species ; in T. whitHeldi of the higher Kas- 

 kaskia the IIBr were reduced to 2, and sometimes also the IIIBr, with an occasional reduc- 

 tion in IBr ; and there the genus ended so far as known. 



In the figures of these four species there is a frequent appearance of straightness in the 

 sutures between brachials which must not be taken as representing the actual facts ; nearly 

 all these specimens have been more or less weathered, and the patelloid projections being 

 very thin, as in the somewhat similar T. intermedins, they have largely disappeared ; careful 

 examination with a magnifier discloses clear traces of them in nearly every specimen, but 

 this is not easily shown in the drawings. 



Types. Author's collection. 



Horizon and locality. Lower Carboniferous, lower part of Kaskaskia Group ; it occurs 

 chiefly in the Platycrinus bed of the Ohara limestone, equivalent to part of the Ste Genevieve 

 formation, but also passes up into the overlying beds equivalent to the Renault. Huntsville, 

 Alabama. 



