130 SIPHONODENTALIIDyE. 



Family SIPHONODENTALIIDJE. 



:^Siphonopoda Sars, GadUince Stoliczka, Siphonudentaliince Tryou, 

 Siphonodentaliidce or Siphonopodidce Simroth. 



Scapliopoda having the foot either expanded distally in a sym- 

 metrical disk with crenate continuous edge with or without a 

 median finger-like projection, or simple and vermiform, without de- 

 veloped lateral processes. The shell is small and generally smooth, 

 often contracted towards the mouth. Other characters essentially as 

 in Dentali'klce. 



Distribution, all seas, almost exclusively in deep water. 



The essential character of this family is in the structure of the 

 foot. In the Dentallidde there is an " epipodial " sheath, which is 

 discontinuous or interrupted on the side toward the head, and emar- 

 ginate or deeply notched on the opposite side, being most expanded 

 laterally ; the foot itself projecting as a well developed conic mass 

 beyond the sheath, and with the subtriangular lateral expansions of 

 the latter, having a more or less trifid or fleur-de-lis appearance. 

 In the Siphonodentaliidce the " epipodium" forms a continuous disk, 

 apparently terminal upon the foot in some forms, like a daisy on its 

 stem ; in others, with a small finger-like median process homologous 

 with the large conic central body of the foot in Dentalium. In Cadu- 

 lus {Helonyx) clavatus (Gld.), as figured by Stimpson, no epipodium 

 of any sort is developed. 



There cannot be much doubt that the shape of the epipodial disk 

 is subject to considerable change during the process of burrowing^ 

 as its hollow or channelled structure is to some extent comparable 

 with that of the foot of Solen and other digging Pelecypods ; but so 

 far as now known, there is no Siphonodentaloid form having the 

 epipodium interrupted dorsally and the foot itself well developed 

 beyond it, as in the Dentaliidoi. 



We know of no family of like extent so imperfectly known ana- 

 tomically as this one. With the exception of some excellent work 

 Ijy the Sars, father and son, a few descriptions by JeflTreys and others, 

 and an outline drawing by Stimpson, no data have been -published. 

 What little is known of the soft parts indicates that important re- 

 sults may be expected from observations on a larger number of 

 species, especially in the genus Cadulus. At present it is only possi- 

 ble to base the genera and subgenera upon characters of the shell. 

 For further anatomical details see the introductory portion of this 

 work, where the distribution of the species is also discussed. 



