712 MR. E. A. SMITH ON SHELLS FROM LAKE NYASSA. [NoV. 6, 



present, although never large ; whilst in the two last-named birds, 

 both from Africa, it is absent on both sides of the body. Such 

 being the case, it seems to me highly probable that the relationship 

 between Abdimia sphetiorhyncha and Xenorhynchus senegalensis is 

 more intimate than that between X. senegalensis and X. australis ; 

 and this view is favoured by their geographical distribution. 



The tendency of the ambiens muscle to vanish in certain of the 

 birds so closely allied as the Storks under consideration, in certain 

 Psittaci, as well as in some of the ColumbEe, is one which our know- 

 ledge of their habits does not enable us to explain. It can have no 

 relation to the habits or bulk of the species ; for this muscle is present 

 in the Ostrich as well as in the smallest Cuckoo, whilst it is absent 

 in the Cassowaries and the Passeres. The fact that it is not found 

 in certain Storks makes its total loss in the Ardeidse less surprising 

 than it would otherwise be. 



6. On the Shells of Lake Nyassa, aud. on a few Marine 

 Species from Mozambique. By Edgar A. Smith. 



[Keceived September 29, 1877.] 



(Plates LXXIV. & LXXV.) 



The British Museum has recently acquired a small series of 

 shells collected by Mr. F. A. Simons at Lake Nyassa, and a few 

 obtained by him at the mouth of the Macusi river, near Quilimaue, 

 on the east coast of Africa. 



Among the former are several very interesting though small 

 species, which, as far as I have been able to ascertain, are unde- 

 scribed. 



As complete lists of species from restricted localities are very 

 useful, I have brought together all those which are known inhabi- 

 tants of the lake. Fourteen, collected by Dr. Kirk, are all that have 

 as yet been recorded ; and now I am enabled to add eleven others to 

 that number. 



Of these the 3Ielania polymorpha is very remarkable, as showing 

 the great variation to which some il/e/a««Ve are subject; and, indeed, 

 I do not feel at all certain that the two forms, M. piipiformis and 

 M. turritospira are not very abnormal growths of the same shell. 



I. Lake-Shells. 

 L Melania tuberculata, Miiller. 



Hub. Lake Nyassa (Simons and Br. Kirk). 



Four specimens of this variable species from the lake differ from 

 the normal and usual form in having the whorls less convex. There 

 is a narrow white zone at the top of the whorls next the suture ; and 

 beneath a pale-olive epidermis the shell is semitransparent, whitish, 

 and ornamented with series of minute red dots. The longitudinal ribs 



