L. Agassiz on the Echinodermata. 447 



A. cingulatus, Goldf. — A. granulatus, Goldf. — A. moniliformis, Mill. — 

 A. murtcatus, Goldf.— A. nodulosus, Goldf. — A. gothlandicus, Goldf. — A. 

 hevis, Mill.— A. polydactylus, Mill. — A. tessellatus, Goldf. — A. iriaconta- 

 dactylus, Mill. — A. tesseracontadactylus, Mill. 



17. Melocrinus, Goldf. — This genus differs from Rhodocrinus 

 and Actinocrinus only in the base of the five rays alternating with 

 five pieces distinct from the summit of the pedicel, and the laminae 

 which close the visceral cavity above being larger than those inclosed 

 between the rays at the point where they separate from the disc. In 

 other respects the structure of the Rhodocrinus, Actinocrinus, and 

 Melocrinus is very similar. The species are fossils from the grey- 

 wacke and carboniferous limestone. 



M. gibbosus, Goldf. — M. Icevis, Goldf. — M, hieroglyphicus, Goldf. 



18. Eucalyptocrinus, Goldf. — Visceral cavity spacious, sur- 

 rounded at its base by five plates which alternate with three series 

 of ten laminae on the edges of which are inserted the rays. One 

 fossil species from the greywacke. 



E. rosaceus, Goldf. 



19. Poteriocrinus, Mill. — Pedicel rounded, pierced by a round 

 canal ; visceral cavity surrounded at its sides by three alternating 

 series of five large hexagonal laminae, the upper of which bear five 

 bifurcate rays composed of elongated articulations. The species are 

 fossils from the carboniferous limestone. 



P. crassus, Mill. — P. tenuis, Mill. 



20. Platycrinus, Mill. — The base of the rays is composed of five 

 large laminae adhering to each other, and alternating with the five 

 distinct pieces of the summit of the pedicel ; the five rays are in- 

 serted at the edges ; between their bases five small laminae may be 

 distinguished ; above these are some very small ones which close the 

 visceral cavity. The species are fossils from the greywacke and 

 the carboniferous limestone. 



PL ventricosus, Goldf. — Pl.granulatus, Mill. — PI. pentangidaris, Mill. — 

 PL rugosus, Mill. — PL striatus, Mill. — PL Icevis, Mill. — PL tuberculatus, 

 Mill. — PL depressus, Goldf. 



21. Cyathocrinus, Mill. — This genus differs from the preceding 

 only by the disposition of the large laminae which surround the visceral 

 cavity, and which are in two series, while in Platycrinus there is but 

 one. Between the bases of the rays we notice a small hexagonal la- 

 mina. The pedicel is either round or pentagonal, furnished with small 

 simple rays. The species are fossils from the greywacke and car- 

 boniferous limestone. 



