MONOGRAPH OF THE EXISTING CRINOIDS. 291 



(1) The basals and orals in the early larva are perisomic plates, not having as yet 

 assumed their ultimate status of primary plates; (2) the plates of the crinoid 

 calyx originated as a development from an integument filled with minute spicules ; 

 and (3) the spicules in such an integument may develop individually into special- 

 ized forms, such as large spicules, rods, scale-like plates, buttons, or anchors, or 

 through plates of the perisomic type into the typical crinoid plates. 



There is an interesting superficial similarity between the side and covering 

 plates in the crinoids and the so-called "snowshoes" developed (from modified 

 feathers) along the sides of the toes of certain grouse in winter (fig. 762, p. 353) to 

 increase the area covered by the feet, and thus to enable them to travel over 

 soft snow. 



TENTACLES. 



In the details of their anatomical and histological structure the tentacles 

 appear to vary but little in the different groups. There is great diversity, however, 

 in the extent to which calcareous deposits are developed within them. 



These calcareous deposits, when present, are always in the form of small 



spicules, sometimes smooth, straight, or bent, but usually roughened or studded 

 with minute spines and more or less irregular. 



The manner of occurrence of these spicules is indicated in the following table : 

 o\ No calcareous deposits in the tentacles: 



Comatella nigra. Amphimetra papuensis. 



Comatella stelligera. Stephanometra monacantha. 



Comatella maculata. Pontiometra andersoni. 



Capillaster sentosa. Oxymetra finschii. 



Capillaster multiradiata. Dichrometra flagellata. 



Capillaster coccodistoma. Dichrometra ddderleini. 



Comissia littoralis. Mariametra subcarinata. 



Comatula pectinata. Mariametra delicatissima. 



Comactinia meridionalis. Lamprometra palmata. 



Comatulides australis. Cenometra delicata. 



Comaster minimus. Cenometra unicomis. 



Comantheria polycnemis. Cyllometra albopurpurea. 



Comanthus pinguis. Decametra parva. 



Comanthus solaster. Prometra chadwicki. 



Comanthus japonica. Oliffometra carpenteri. 



Comanthus trichoptera. Cosmiometra orassicirra. 



Comanthus annulata. Tropiometra macrodiscus. 



Zygometra microdiscus. Tropwmetra afra, 



Zygometra elegans. Tropiometra carinata. 



Catoptornetra magnified,. Tropiometra picta. 



Himerometra martensi. Tropiometra indica. 



Bimerometra magnipinna. Antedon petasus. 



Himerometra robustipinna. Antedon bifida. 



Eeterometra, crenulata. Antedon adriatica. 



Eeterometra pulchra. Toxometra paupera. 



Bomalometra denticulata. Eumetra chamberlaini. 



Amphimetra spectabilis. Iridometra adrestine. 



Amphimetra discoidea. Iridometra melpomene. 



