74 saxxcavid^:. 



species of Saocicava which excavates holes in calcareous 

 rocks or sandstone will, failing such materials, or for 

 other reasons which are at present unknown to us, spin 

 a bvssus and thus fix themselves in the chinks and cran- 

 nies of harder rocks, or now and then inside old bivalve 

 shells. 



Genus I. PANOPE'A*, Menard de la Groye. 



PL III. f. 2. 



Body oval, fleshy : tubes very long, united nearly through- 

 out, and enclosed in a tough leathery sheath : gills long : foot 

 short, stout and muscular. 



Shell equivalve, wrinkled transversely, gaping widely at 

 both ends but much more so at the posterior end : epidermis 

 thin: ligament short, prominent, attached to a process of the 

 hinge-plate, which extends as the shell increases in size, and 

 is sometimes triangular or represents the arc of a circle : tooth, 

 a small conical cardinal in the right valve fitting into a cavity 

 in the left valve : pattial scar entire, not deeply sinuated. 



Most British conchologists are better acquainted with 

 the large and scarce shell usually known as "Panopcea 

 Norvegica " (but which, as I have before remarked, is a 

 species of Saxicava), than with the small shell which I 

 consider a true Panopea. Although the animal of this 

 latter species is as yet unknown, the peculiar form of 

 the shell, the structure of the hinge, and the pallial scar 

 present the same characters which belong to P. glyci- 

 meris (or Aldrovandi) and its numerous congeners. 

 The animal of P. australis was described by Valen- 

 ciennes in the ' Archives du Museum d'Histoire natu- 

 relle ' for 1839, and that of P. glycimeris by Woodward 

 in the i Proceedings of the Zoological Society ■ for 1855. 

 The former likened it to that of My a arenaria, and was 

 of opinion that the labial palps are olfactory organs. 



* A Sea-Nymph. 



