FASCICULATED. 147 



partly internal, passing through the hinge on a somewhat raised, 

 callous area in the lower valve. Muscular impressions elongated, 

 two in each valve, united by a slender palleal impression. Rivers 

 of Africa. — Obs. The irregular, unequal air-bubbles of the inner 

 surface, whence this genus derives its name, are very brilliant in 

 some species, and atone, in some measure, for the rugged 

 ugliness of the exterior. In its irregular form, foliated structure, 

 and toothless hinge, it resembles Ostrea, from which it differs in 

 having two muscular impressions. Fig. 155, E. semilunata. 



EULIMA. Risso. Fam. Scalariens, Lam. — Descr. Elongated, 

 smooth, pyramidal ; spire long, composed of numerous whorls ; 

 apex acute, slightly tortuous ; aperture oval, rounded anteriorly, 

 acute at the posterior union with the body whorl ; outer lip 

 slightly thickened ; columella smooth. Fig. 347, E. labiosa, 

 fig. 348, E. splendidula. A complete illustrated monograph of 

 this genus of pretty shining little shells, consisting of 1 5 known 

 species, is given in parts 52 and 53 of the Conchological Illustra- 

 tions by the author. 



EUOMPHALUS. Sow. Fam. Scalariens, Lam.— Descr. Orbi- 

 cular, planorbular spire, with three or four volutions, imbricated 

 above ; smooth below ; aperture of a round polygonal form ; 

 umbilicus large, penetrating to the apex of the shell. — Obs. 

 This genus of fossils very nearly resembles Delphinula. The 

 main difference appears to be that the whorls do not increase so 

 rapidly in size in the former as in the latter. Fossil, in the Car- 

 boniferous Limestone. Fig. 350. 



EXOGYRA. Sow. A genus of fossil bivalves, resembling Chama 

 in shape and Ostrsea in structure, having but one muscular 

 impression in each valve. Fig. 183. 



EXSERTED. Standing out, protruding. 



EXTERNAL. An external shell is one which contains the animal, 

 and is not covered by the mantle. 



FASCIATED. (fascia, a band.) Banded or striped. Ex. Carocolla 

 marginata, fig. 277. 



FASCICULATED, (from fasciculum) A little bunch of hairs or 

 l 2 



