Introduction to A nimal Morphology. 1 3 1 



arms long, close, four (five, Ag.) pair; these, like 

 the last, are West Indian. 3. Ophiocrinus with five undivided 

 arms, sixteen ventral cirrhi, and no other ossicula. 4. Rhizo- 

 crinus with a long, jointed column, and long rounded joints ; 

 calyx variable in its number of pieces ; anus circular, midway 

 between the mouth and the margin of the disc (North Atlantic). 

 CYmiatulidse feather stars; free when mature; stalked 

 when young; body with immovable dorsal cirrhi of 2-180 

 joints, representing those of the stem in Pentacrinus ; 10-40 

 pinnulated arms ; anus ventral. They quickly pass through 

 the early stages of development, when they appear as ovate 

 bodies with four transverse rows of cilia, a keyhole-shaped 

 mouth and an anus. The stalked condition has been named 

 Fhytocrinus. The genera are Antedon, the common feather- 

 star, from which possibly Alecto may be distinct ; and Pha- 

 nogenia, with a simple stelliform centro-dorsal joint, and basal 

 plates hidden, internal (from Malacca). Allied, are the fossils 

 :-tha, Pterocoma, &c. 



4. Ophiuroidea brittle stars, with rounded or pentagonal 

 flattened discs, and elongated arms differentiated from the 

 body, and containing no viscera. The ambulacral pedicelli 

 have no ampulla? nor sucking discs, and feet are developed 

 medio-ventrally. Pedicellarue are wanting. There is a cal- 

 cified peristome of oral plates, grooved for the nerve ring, 

 and armed with fijlac an^ularcs, or spurious teeth, based on 

 small plates (tori angularaF), one at each of the five 

 of the mouth. The disc may be naked (Ophiomyxa, 

 Opl ::); or covered with fine, hard, equal granules 



(Ophiocoma, Ophiarachna) ; or with shields (Ophiomastix) ; 

 - (Ophiothrix) ; or many large, symme- 

 trical shields (Ophiolepis). The arms are special locomotive 

 1 in four rows of plates, dorsal, ventral, 



and two lateral, within which is an axis of jointed, squarish, 



derma!. : .irated fr<m the ventral surface 



shieKN by tin: ambulacra! VCSSel, and above the axis is the 



'h j>late consists of two ank\l>sed halves 



1 there is a branch of the nerve and water vessel for each 



joint of the axis The first pair of axial segments is! 



lii of Kcliini (?) 



