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Sp. 4. Esraeria Brasitiensis, Nobis. (Pl. XI. f. 4, 4a, 40, 4c.) 
Carapace-valves elongately obovate and pisidiform. Anterior ex- 
tremity much broader than posterior, much more convex, and gaping. 
Beaks prominent and situated near anterior extremity. The shell 
is of a uniform dull horny colour and appearance externally and in- 
ternally, very thin and translucent. Ribs numerous, elevated and 
smooth. The intermediate spaces are slightly concave, and appear 
roughened all over with numerous very small dots. This is a larger 
species than the preceding, and is much more elongated in form,—not 
possessing the fine polished appearance which distinguishes it, but 
appearing as if covered with a very thin epidermis. 
Hab. Brazil, Mr. Sowerby. Brit. Mus. 
Sp. 5. Estaeria Dawavacensis. 
HE. Dahalacensis, Riippell & Straus, Mus. Senkenberg. ii. 119. 
t. 7. f. 1-15. 
Carapace-valves irregularly quadrilateral. Anterior extremity 
slightly rounded, posterior extremity cut sloping or with beveled 
edges. Dorsal and ventral margins both straight. Beaks rather 
prominent, placed near anterior extremity. The carapace is of a 
light horny colour and lustre, both internally and externally, and 
translucent. The ribs are about 14 in number and rather prominent. 
The spaces between them are slightly concave and covered with very 
numerous exceedingly minute raised dots or punctations, and a good 
many much larger intermixed. 
Hab. Dahalac, Abyssinia, Riippell. Mus. Dom. J.O. Westwood. 
B. Valves of carapace longitudinally striated on their surface. 
Sp. 6. EsrHerra ponacirormis. (Pl. XI. f. 5, 5a, 54, 5c.) 
Nuculina donaciforme, Parreyss MSS. in Mus. Brit. 
Carapace-valves shortly obovate and pisidiform ; anterior extremity 
broader than posterior, more convex but not gaping; beaks pro- 
minent, placed near anterior extremity ; the carapace is quite opake, 
of a light brownish yellow externally, of a dull lustre and with a spot 
of dark purple and of a metallic lustre on the anterior margin and on 
the dorsal edge behind the beaks; the interior is of a beautiful 
shining lustre and of a deep purple colour ; the ribs are numerous 
and rather unequal; the spaces between them are striated longitu- 
dinally ; the strize, when examined by the microscope, being irregular 
and of a somewhat complicated structure, near the edge of the rib 
frequently forraing loops and running one into the other. 
Hab. Abeid, Kordofan, Parreyss. Sent to the British Museum 
Collection as a species of mollusk belonging to the genus Nuculina, 
and called Nuculina donaciforme. 
Sp. 7. Esrneria Boysu, Nobis. (Pl. XI. f. 6, 6a, 63, 6c.) 
Carapace-valves broadly obovate; anterior extremity convex, gaping, 
much broader than the posterior, which however is rounded and 
obtuse ; beaks prominent, placed near anterior extremity ; carapace 
opake ; externally of a dull shining grey colour, with the anterior 
