C M.AMociMM S DIOMED I 



Judging from the analogy of the condition of the top stem joint in Cala- 

 mocrinus, and the formation of a new joinl between it and the I 

 Carpenter is evidently correcl in attributing the variation in the thickness 

 of the top stem joints in the specimens of Millericrinus Pratti which he 



examined to a secondary deposition of limestoi utside the upper stem 



joints. I have been unable in Calamocrinus to trace an\ sign of pits 

 between the basals and radials, the so called "ovarian openings" of 

 Carpenter. 



Billings also figures the stems of a number of palaeozoic Crinoids, show- 

 ing, as in Heterocrinus (Geol. Survey. Decade I. Plate IV. Fig. 5 a ) and in 

 Dendrocrinus (Plate III. Fig. 7"), the young joints crowded at the tipper 

 pari of the stem. Intercalated joints are shown in some of his figures, 

 as Rhodocrinus (Plate VI.) and Glyptocrinus (Plate VII. Figs. 2 b , 2 d , Plate 

 VIII. Fig. l b ). 



In one specimen of Heterocrinus kindly lent me by Messrs. Wachs- 

 muth and Springer, the outer edge of the wedge-shaped new joints are 

 plainly seen forcing their way out between the basals and the top stem 

 joint, and between the sutures of the succeeding joints. In another, the 

 wedges of the new joints, which are thin and disconnected on the lines 

 of sutures near the upper part of the stem, gradually become wider, and 

 form a very thin joint alternating with a stouter one; and still lower down 

 on the stem these new intercalated joints become thicker, but they still 

 show a marked difference in their diameter and height when compared 

 with the older stem joints. 



In a specimen of Ectenocrinus with a tripartite base, the young joints 

 at the summit of the column appear to alternate irregularly from side to 

 side. These irregular wedges do not anchylose and form a single joint 

 extending across the stem, so that the inequality of growth of the two 

 sides of the stem or of the wedges themselves may account for the dis- 

 jointed wedges which are not unfrequently found in the stems of many 

 fossil Crinoids. 



In a specimen of Glyptocrinus belonging to the Wachsmuth and Springer 

 collection, we find a small lobed ring with radiating ridges inside of the 

 basal ring. 



In specimens of Cyathocrinus, the top joint is seen from the under side 

 within the infrabasals. This youngest joint is a small lobed disk resting 

 upon ridges and grooves, and not extending as yet, in the specimens exam- 



