524 TEST ACE A ATLANTIC A. 



Habitat S. lago ; in rivulis a cl. Dohrn repertus. 



Judging from two examples of this Ancylus which were 

 given to me by Dohrn, it is at once separated from the species 

 of the Canarian and Madeiran archipelagos by its small size (it 

 being only a line in length) and rather narrowed contour, by its 

 thin subhyaline texture and pallid hue, and by there being 

 scarcely any indication (so far as I can detect) of radiating 

 costae on its surface, where, nevertheless, the hair-like spiral 

 lines are quite distinguishable and closely set. 1 Moreover in 

 the types before me, the apex (behind which there is a short 

 central obsolete channel or groove, quite traceable when the 

 shell is viewed obliquely) is just perceptibly tilted or eccentric ; 

 but this may be only accidental. 



The A. Mitteri is from the island of S. lago, where it was 

 detected by Dr. H. Dohrn. 



GASTROPODA (PECTINIBRANCHIATA). 



Tarn 7. KI880IDJB. 

 Genus 16. HYDROBIA, Hartm. 



Hydrobia acuta. 

 Cyclostoma acutum, Drap., Hist. Nat. des Moll. 40. t. 1. 



f. 23 (1805) 



Paludinella sp., Dohrn, Mai. Bldtt. xvi. 20 (1869) 

 Hydrobia acuta, Morel., Journ. de Conch, xiii. 243 (1873) 



Habitat S. Nicolao ; in Ribeira de Castelhoens a cl. Dohrn 

 copiose lecta. 



This common European Hydrobia was found abundantly by 

 Dohrn in the Ribeira de Castelhoens in the east of S. Nicolao ; 

 but, owing to an unfortunate accident, he lost the whole of his 

 examples except one, so that he did not feel justified in 

 attempting to identify the species positively from a single indi- 

 vidual. It would appear however that a further supply must 

 have been obtained by MM. Bouvier and de Cessac, for Morelet 

 was enabled to give the information which Dohrn could not ; 

 nevertheless he does not tell us so, nor indeed does he even 

 mention in which island the fresh examples were met with. 

 This is much to be regretted, for the following observations 

 would certainly seem to indicate that additional material had 

 come to hand since Dohrn's paper was published: 'Cette 



1 Dohrn's remark on his A. Milleri is, that it < differs from all the dextral 

 species of the Old World in the longish-ovate shape of its aperture, and in 

 its total freedom from any radial ribbing.' 



