320 A. E. Verrill — North American Ophiuroidea. 



The teeth are stout, flattened, obtuse; they vary from three to 

 eight in number. 



The internal structure of the mouth-parts and arms is much like 

 that of some of the A7n2)hiuridce. The "jaw-i^lale" or dental plate 

 is generally separate from the jaws, and the three parts of the peris- 

 tomial plates are generally distinct, but they are united in Ophioca- 

 max. 



The genera Ophioplax and Ophiolebes are, in several characters, 

 more or less intermediate between the two groujss, both externally 

 and internally. 



This family, as here understood, includes the following genera : 

 Ophiacantha^ Opliioinitra^ Ophiotrema, Oj)hiocamax, Ophiolebes, 

 OpJiiothamnns, Ophiocopa, Ophiochiton, Ophiotoma, and probably 

 Ophiohlenna. To these I have recently added several others, 

 enumerated below, separated from Ophiacdfitha, Ophiomitra, and 

 Ophiopsila. 



The first six of those named above have the disk covered with 

 scales bearing spinules or thorny processes, or sometimes granules. 

 Ophiochiton and Ophiocopa have naked or nearly naked scales. 

 Ophiohlenna and Ophiotoma are covered with naked skin. The 

 radial shields may be large or small, concealed or exposed. 



Ophiacantha Miill. and Troscliel, 1843. {sens, ext.) 



The species of this genus, taken in the extended sense, are very 

 numerous in all seas and are diflicult to determine. They are 

 abundant in deep water in northern latitudes, as well as in tropical 

 seas. Ten or eleven species are known off the coasts of New Eng- 

 land and Newfoundland. Several of them occur only at great 

 depths. About twenty species, including two described as new in 

 this article, are known from the West Indian fauna. 



This genus is very remarkable for the great variations in the 

 armature of the disk. Some species have only rounded granules ; 

 others well-formed tapered spines ; others short, thornj^ stumps ; 

 others small bifid or trifid spinules or ci'otchets ; while many species 

 have mixtures of two or more of these sorts. 



It is probable that these structures have been developed as protec- 

 tive organs, in accordance with the ordinary laws of Natural 

 Selection, and that they are, therefore, directly correlated with the 

 habits of the various species. But the habits of many species are 

 not yet known. I have found several species clinging to gorgonian 



