1916] The Ottawa Naturalist 111 



possible to diagram these brachioles so as to suggest a uniserial origin, 

 and this is true also of the so-called pinnules of Caryocrinites, the 

 ossicle in contact with the lower brachial being regarded the first. 



The pinnulars of Caryocrinites are long and narrow in a direction 

 parallel to the length of the pinnule, and are arranged in alternating 

 series, as already indicated. The covering plates are long and narrow 

 in a direction transverse to the length of the pinnule, about three or 

 four occurring in the length of one pinnular. 



The arms of Caryocrinites apparently varied in length. In an 

 individual having a theca 30 millimeters in height, the arm nearest the 

 left side of the anal opening has a length of 55 millimeters, while the 

 second arm anterior to the latter, but on the same side- evidently was 

 considerably longer since the part remaining, lacking the tip, is 75 

 millimeters in length. Possibly the posterior arms were shorter than 

 the anterior arms also in other specimens. 



The number of arms attached to the same theca varies in number 

 in different individuals. In the youngest specimens, of which two 

 occur in the Springer collection, the facets for 3 arms are distinctly 

 developed- In one of the largest specimens, 14 arms are present. 

 These are arranged in three groups, the anterior and left posterior 

 groups including 5 arms- while the right posterior group includes only 

 4 arms. This varies in different individuals. 



The question arises how and where the additional arms arise. It 

 is noticed that in addition to the facets supporting the arms, the theca 

 presents also smaller depressions, apparently for the attachment of 

 appendages. Some of these depressions are traversed by a single 

 median ridge placed in a radial direction, suggesting former articula- 

 tion with some appendages. While no appendage actually ever has 

 been found attached to these depressions it has been noticed that the 

 order of appearance of these depressions is also the order of appearance 

 of the additional arms, when a comparative study is made of the larger 

 and smaller specimens of the same species. From this it is evident 

 that these depressions are the points of ertiission of the additional arms. 



Since similar 'depression^ are present even in the largest speci- 

 mens, and the position of these, of course, is never occupied by arms, it 

 is possible that some of the later appendages were never strongly 

 articulated with the theca, probably always remained comparatively 

 small, and were specialized for the purpose of bearing the genital 

 glands. Jaekel (Thecoidea und Cystoidea, 1899, p. 302, fig. 70) 

 figures the relative position of the arm bases and of the smaller open- 

 ings. Wachsmuth and Springer, (1881, Revision of the Palaeocrinoidea, 

 Proc. Philadelphia Acad. Nat. Sci., vol. II, p. 51), long ago called 

 attention to similar small depressions or pores at the sides of the arm 

 facets of Batocrinus, and suggested respiratory purposes. 



The area of attachment at the base of the column of Caryocrinites 



