110 The Ottawa Naturalist [December 



specimens pores exist along the sutures between the plates, either a 

 single pore at the middle of each side, or two pores along each side, 

 close to the radial ridges extending to the angles of the plate. Half of 

 each pore occurs on half of each of the adjoining plates. It has not 

 been proved, however, that these pores are open in un weathered 

 specimens. They may be covered by the epistereom, as in the case of 

 the pores of Comarocystites. In Canadocystites, neither pores nor 

 vertical mesostereom lamellae are present. This difference in plate 

 structure in the three genera is remarkable in view of the close relation- 

 ship suggested by the structure of the food-groove system. Owing to 

 the entire absence of true pectinirhombs, notwithstanding the suggestive 

 structure of the thecal plates of Comarocystites, the separation of these 

 three genera from the Rhombifera seems desirable. Regarding Malocys- 

 tites, which appears related to Canadocystis, too little is known at 

 present. The recumbent food-grooves extend over the upper surface 

 of quadrangular plates arranged in uniserial order, but it is not known 

 whether the pinnules were attached in a single row, and whether the 

 pinnulars were arranged in uniserial order or not. 



V Addenda. 



27. Notes on Caryocrinites ornatus Say. In Caryocrinites 

 ornatus both the brachials and pinnulars are biserial in arrangement 

 (Plato IV' figs. 4, 5). This was recognized by Hall (Pal. New York, 

 2, 1852- p. 219, pi. 40, figs. 1 i, k, m), although he did not get a clear 

 idea of the structure of the pinnules from his specimens- Much better 

 material is present in the collections of Frank Springer, in the U.S. 

 National Museum, at Washington, and this material has been placed 

 freely at the disposal of the writer. Compared with the length of the 

 arms, the pinnules are very short. In a specimen, with a theca 30 

 millimeters in height, the pinnules attached to an arm 55 millimeters 

 in length were 4 millimeters long. In another specimen, with a theca 

 12 millimeters in height, and with arms from 36 to 40 millimeters in 

 length, the pinnules were only 3.5 millimeters long (Plate IV, fig. 4). 

 In this specimen, each of the two series of pinnulars rests upon a 

 separate brachial' 'the lower brachial of each pair being shorter. 'In 

 other specimens, however, the shorter brachials occasionally are reduced 

 to mere transversely elongated vestiges remaining between the hori- 

 zontal sutures separating the larger brachials, and in those cases the 

 two series of pinnulars rest practically against the same brachial- 



Since typical crinoidal pinnules should present only a single row 

 of pinnulars, it might be emphasized that these so-called pinnules of 

 Caryocrinites are not homologous to the pinnules of crinoids, but to the 

 brachioles of cystids. These- brachioles, among the Rhombifera and 

 Diploporita, are uniformly biserial, the individual ossicles alternating 

 in position across the width of the brachiole. As a matter of fact, it is 



