36 CALAMOCEINUS DIOMED^. 



opening come closely together in P. naresianus and in P. decorus. In the 

 former the plates round the mouth are larger, and they entirely conceal 

 the opening; while in other species there is a broad bare area, forming 

 eight to ten or more angles bounded by small plates. There are no pores 

 drawn in the anal interradium of P. Wyville-Thomsoni, as in Calamocrinus. 

 The continuation of the perisomic plates along the arms is best defined in 

 P. naresianus. 



The lower rows of plates of the anal interradium are similar .to those 

 of the other interradii ; but they rapidly pass into longer and larger plates, 

 which again diminish rapidly in size towards the extremity of the anal 

 proboscis (Plate II. Figs. 1, 2, 4, Plate III. Fig. 5, Plate V. Figs. 2, 3, Plate 

 VI. Fig. 1), and around the small anal opening they are stout plates be- 

 coming almost papillte, but all imperforate. 



The interradial plates protecting the anal proboscis seem to differ as 

 much in size and shape in the different specimens as the interradial plates 

 of the rest of the calyx ; in one case they are much smaller and more 

 numerous in proportion to the size of the anal proboscis (Plate III. Fig. 3) 

 than in the anal proboscis figured in Plate II. Figs. 2, 4. 



The anal proboscis in all the specimens is placed close to the oral aper- 

 ture. The anal proboscis was evidently capable of but slight movement, 

 being for more than half its length rigidly soldered to the edge of the 

 adjacent arm and pinnule joints (Plate II. Figs. 2, 3, Plate III. Fig. 3, Plate 

 V. Figs. 2, 3, Plate VI. Fig. 1). The upper third alone was capable of a 

 certain amount of lateral and of vertical movement. The anal proboscis 

 of the specimen shown in Figure 3 of Plate III. was proportionally longer 

 than those of Plate VI. Fig. 1, and Plates II. and III. 



It is interesting to compare the descriptions by D'Orbigny and de Lo- 

 riol of the interradials of the fossil ApiocrinidjB ; for in some of the 

 species of the genera Guettardicrinus and Apiocrinus the presence of 

 stout interradials and their close union with tlie rays, which tend to 

 increase the size of the cup, present many points of resemblance to the 

 Tessellates. 



In Guettardicrinus, Apiocrinus, Uintacrinus, and Calamocrinus, the in- 

 terradials extend be3'ond the axillaries. The arms of Guettardicrinus 

 are united as far as the second brachial, either directly or by interra- 

 dials. In Apiocrinus Parkinsoni the second and third radials are in close 

 contact. 



