SHALLOW-WATER STARFISHES 2$ 



Adambulacral plates are generally short and crowded, equal in 

 number to the ambulacrals. They may each bear a single spine 

 (monacanthid) , or two spines (diplacanthid) , or alternately one and 

 two (subdiplacanthid) , or rarely three spines (triplacanthid) . 



The superior and inferior marginal plates are rather small 

 (cryptozonial) , but are generally distinct and bear spines, often 

 longer than those on the dorsals. In some Brisingida one row, or 

 rarely both rows, may be lacking. They extend to the apical plate 

 and increase in number during the whole period of growth by the 

 addition of new plates next to the apical. 



The dorsal skeleton is variously constituted, but usually consists 

 of plates and ossicles, often very unequal in size and form, so united 

 as to move freely, leaving many papular areas between them. In 

 some of the Brisingidae and in Pycnopodia the ossicles are mostly 

 nearly abortive, roundish, and isolated in the integument. 



The plates generally bear spines, either singly or in clusters; 

 sometimes they are reduced nearly to the form of granules ; never 

 paxilliform. The papulae may be few, or many in large clusters. 

 They usually occur both on the dorsal and on the ventral surfaces, 

 adetopneusic arrangement. 



The Forcipulosa, as the name indicates, are especially character- 

 ized by the presence of very peculiar, pincer-like, two-bladed pedicel- 

 lariae, usually of two forms, movably attached to the dermis of the 

 spines, or to the surface between, by means of longer or shorter 

 flexible dermal pedicels. 



VARIOUS KINDS OF PEDICELLARIJE. 



Except possibly in a few rare cases, and in quite immature speci- 

 mens, at least one form of these is always present. 



Of the two principal forms, those known as forcipate or " minor 

 pedicellarice" are the most abundant and occur most constantly. 

 Such pedicellariae do not occur on starfishes of any other order. 

 Those nearest analogous occur on certain Echinoidea. 



In the larger kind, called "major pedicellaria" by Stimpson; 1 



*I prefer to use ordinarily the names first given by Stimpson, in 1861, for 

 the two principal forms of pedicellarias, viz., major pedicellariee and minor 

 pedicellaria. These terms are sufficiently descriptive, and not so liable to be 

 confused as those proposed later by Herapath, though the latter have some 

 advantages. It is desirable, however, to have some additional special de- 

 scriptive terms for varieties of each sort. Either form may be attached to 

 the spines or to the general integument. The minor pedicellariae that sur- 

 round spines in wreaths, may be called circumspinal; those in smaller irregu- 

 lar clusters on the spines, epispinal; those attached to the general surface of 



