48 CALAMOCRINUS DIOMED.E. 



of the stem belonging to Figure 8, in which the very prominent transverse 

 ridges had passed into merely angular sides of the column. 



Comparing the outline of these stems with similar parts in fossil species 

 of Apiocrinus, Guettardicrinus, and Millericrinus, we find that the serrations 

 of the suture of the basal part of the stem of Calamocrinus are closer than 

 those of Apiocrinus or their fossil allies, the suture being generally a double 

 line showing the closest kind of reticulated structure. See the drawings of 

 the upper part of the joints, Plate XVII. Figs. 1, 9, 10. The median part 

 of the stem resembles somewhat the stem of those species of Millericrinus 

 in which the sutures were nearly smooth, without the tendencj' to form an 

 angular stem, while the upper parts of the stem, with its prominent ridges 

 and flat rings intervening (Plate XV^II. Fig. 5) between them, remind us 

 very strongly of a similar structure in the stems of several species of 

 Millericrinus. 



The stem both of Guettardicrinus and of Apiocrinus is smooth, the ar- 

 ticular face of the former being, like that of the basal part of the stem of 

 Calamocrinus, flat, with a large number of ribs, here and there bifurcated. 

 But the median parts of the stem, as well as the upper parts close to the 

 calyx, resemble more the structure of the stem of Millericrinus in the man- 

 ner in which the upper stem joint is connected with the calyx, as well 

 as in the ornamentation of parts of the stem in the ribbed and flat joints, 

 which however in Calamocrinus shows no trace of being pentagonal, as is 

 the case in many species of Millericrinus. Nor is the ornamentation of the 

 stem as varied as it is in that genus, being limited to the few granules 

 in certain of the rings of the upper part of the stem, to the differences 

 in the character of the transverse rib of the joints in different parts of 

 the stem, and to the serration of the sutures due to the size of the ribs 

 uniting the articular faces of the stem joints. 



There Avere probably eight joints of the upper part of the stem (Plate 

 XVIII. Fig. 2) crushed, and its condition indicates that these joints un- 

 doubtedly formed the part of the stem immediately in contact with Plate 

 XVIII. Fig. 1. The upper stem joints of this specimen were smooth, with 

 slightly undulating articulations, forming a somewhat indented outline, the 

 eight upper joints measuring 7.55 mm. in height. The diameter of the 

 upper stem joint is 0.1 mm., while the diameter of the stem at the sev- 

 enth joint is only 5.50 mm., showing a greater tendenc}' toward a widening 

 in the upper part of the stem than in Plate XVII. Fig. 1, but a fiir less 



