56 Zoological Society. 



Sp, 4. EsTHERiA Brasiliensis, Nobis. 



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, Mi'. Sowerby. Brit. Mus. 



Sp. 5. E&THERIA DaHALACENSIS. 



E. Dahalaeensis, 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 

 transhicent. The ribs are about 14 in number and rather prominent. 

 The spaces between them ai-e slightly concave and covered with very 

 numerous exceedingly minute raised dots or punctations, and a good 

 many much larger intermixed. 



Hab. Dahalac, Abyssinia, Ruppell. Mus. Dom. J. O. Westwood. 



B. Valves of carapace longitudinally striated on their surface. 



Sp. 6. EsTHERIA DONACIFORMIS. 



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 strife, when examined by the microscope, being irregular 

 and of a somewhat complicated structure, near the edge of the rib 

 frequently forming loops and running one into the other. 



Hab. Abeid, Kordofan, Parreyss. Sent to the British Museum 

 Collection as a species of moUusk belonging to the genus Niicidina, 

 and called Nuculina donaeiforme. 



Sp. 7. EsTHERiA BoYSii, Nobis. 



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 coloiir, with the anterior 



