MITRID^. 169 



is rarely exserted when they are crawling and lively, but as they 

 become languid after capture it becomes distended with water 

 and protrudes considerably. When irritated, some species of 

 Mitra emit a purple fluid having a nauseous odor. 



The Philippine Islands would seem to harbor the greatest 

 number of these elegant and beautiful shells, although a great 

 many species were obtained by Mr. Cuming in tropical America. 

 The}' appear to be chiefly confined to the equatorial regions, 

 scarcely any being natives of cold climates. The transversely 

 ribbed species are frequently found in very deep water, and many 

 have been dredged in twent};- and thirty fathoms at the Sooloos 

 and in the China Sea. 



The Mitridse inhabit various stations ; many being strictly 

 reef shells, where the^^ lurk in holes and crevices under sea- 

 weed, but are most generally concealed under stones and blocks 

 of dead coral. Others burrow in sand or sandy mud at various 

 depths ; some delight in stony ground inside the reefs, where 

 they remain concealed under clumps of coral during the day, and 

 like the sand species are nocturnal in their habits. 



Although M. Quoj^ has rightly termed the Mitra an " animal 

 apathique," the small longitudinally ribbed species crawl about 

 pretty briskl}^ over the smooth sand among the low coral islands. 

 The Mitra episcopalis (Iv, 36), probably on account of the small 

 size of its locomotive disk, and the ponderous nature of its 

 long shell, is, however, a very sluggish moUusk. Some of the 

 Auricula-shaped Mitres that live among the Philippines, in the 

 shallow pools left by the receding tide, crawl about the stones 

 out of the water, in company with Planaxis and Quoyia. The 

 Mitres, like many of the large Yolutes, prefer, however, to asso- 

 ciate together, and ma}^ be seen in dozens crawling over the 

 sandy mud-flats in shallow water, being most active just as the 

 flood-tide makes. When the tide recedes, they bury themselves 

 superficially in the yielding soil, and are with difficulty dis- 

 covered. Some of the small ribbed species cover themselves 

 entirely with the sandy mud, and in that disguised condition 

 travel about with comparative security. 



MITRA (typical). Mitriform, thick, spire elevated, apex sharp ; 

 mouth rather small and narrow, notched in front ; columella 

 obliquel}' plicate ; lip rather thick, smooth within. 



[voLUTOMiTRA, Grray. Separated from Mitra on account of 

 the peculiar dentition of an Arctic species, V. Grosnlandica. 

 Twenty additional species have been included in the group by 

 H. and A. Adams ; they are all Mitras in appearance, and the 

 dentition of none has been examined, except that of V. cornea, 

 which decidedly difiers from V. Grcenlandica, and is of the 

 regular Mitra type.] 



AiDONE, H. and A. Adams. Shell fusiform, smooth, polished, 



12 



