LECANOCRINIDAE 165 



(?) Anisocrinus irregularis n. sp. 



Plate X, figs. 5-6 



Lecanocrinus macropetalus, Angelin, Icon. Crin. Sueciae, 1878, p. 12, pi. 19, fig. 3; pi. 22, fig. 24. 



A rather large species, superficially resembling- A. interradiatus. Crown 

 low, broadly subovate, rounded and ventricose below; cylindrical and truncate 

 above, widest about top of RR, where height to width is about i to 2. Surface 

 smooth. Crown about 20 mm. high by 16 mm. wide, but somewhat flattened. 



IBB unknown. BB about as large as radials. RA absent. Anal x very 

 large, and it may be followed by a small triangular plate. iBr similar in form 

 and size to anal, with similar minute plates sometimes following filling the inter- 

 radius. RR large; height of B to R to IBr, 5.5 -.4: 1.7. IBr one-third as high as 

 wide. IIBr, 4, with one or two bifurcations following. Rays uniting closely 

 above iBr, dividing unequally, the branches toward the inside of the dichotom 

 being about three-fifths the width of the outside ones; the subordinate branches 

 parallel to the others, closely abutting to them and to each other, and infolding 

 squarely above the second ramule. Column unknown. 



I have proposed this species for the reception of the specimen figured by Angelin as 

 Lecanocrinus macropetalus in the Icon. Crin. Suec, plate 19, figure 3 and plate 22, figure 24, 

 together with another imperfect one since found, both of which are figured herein. In both 

 specimens the base is broken away, but the other characters are all shown. In the absence of 

 a radianal and the unequally bifurcating arm it presents characters which, if constant, would 

 require the reference of this form to a new genus. But the radianal seems to be a somewhat 

 unstable structure in this genus, having already been found in a variety of positions ; and the 

 arm branching is not quite regular, there being some variation in this respect even in A. inter- 

 radiatus where the bifurcation is not always equal. The specimens here described possess 

 the characteristic facies of Anisocrinus so strongly, that in the absence of abundant corrobora- 

 tive evidence of constancy in the erratic characters it seems best to retain them within this 

 genus; treating it as a highly specialized type in which, with the predominance of its rela- 

 tively enormous interbrachial, other characters become inconstant. 



Type. In the Riks Museum, Stockholm. 



Horizon and locality. Silurian, Wenlock Group, horizon f ; Gotland, Sweden. 



