308 A. E. Verrill — North American Ophiuroidea, 



The genus Amphiin'a, as here adopted, agrees nearly witli the 

 typical genus, as restricted by Ljungman in 1867. Mi'. Lyman also 

 stated that this should be the typical group, in case the genus were 

 to be divided. This restricted genus still includes over sixty species, 

 vv^ith a considerable diversity of structure, as the following table will 

 show. The species are found in all seas and at all depths. 



The arms are generally long and slender, tapering very gradually, 

 and very flexible. 



Many of the species, perhaps nearly all, live buried in the mud 

 and sand of the bottom, or concealed in crevices or under stones, 

 etc. When buried in the mud they usually project the tip of one or 

 more of the arms above the surface of the mud. 



This habit of living concealed is doubtless correlated with the 

 absence of disk-spines for protection, and with the lack of special 

 imitative colors. 



Many of the species have plain, dull colors, resembling the color 

 of the sea-bottom where they live. A. Otteri, from deep water, is 

 plain salmon or light orange. Such colors are j^rotective in deep 

 water. 



AmpMiira [restricted): Table of the species inhabiting the West 



Indies and adjacent loaters, and the Atlantic Coast 



of North America* 



The characters given in this table are those of the adult specimens, 

 or at least of the largest described and figured. The young speci- 

 mens often have fewer arm-spines and differ in other particulars. 

 The number of arm spines given is that of the fully developed joints, 

 towards the base of the arms. The number of spines is also liable 

 to vary in adult specimens. Characters not named in the table, such 

 as the shape of the oral shields, i-adial shields, arm-plates, etc. are 

 often of more value in determining the species than some of the 

 characters mentioned, and should always be considered. They are 

 not all easily utilized in a condensed table like this. 



I. — Disk covered with naked scales. 



A. — Tentacle-scales present. Radial shields divergent, their distal 



ends separated, or scarcely touching. 

 B. — Tentacle-scales two to a pore. 



* In the table, the species that are entirely northern in their distribution are 

 designated by an asterisk. 



