82 Dr. 0. A. L. Morch on the History of Dreissena polymorpha. 



and shortly barrel- shaped, and the last is spirally concave or 

 slightly grooved or channelled a little way backwards from the 

 outer lip below the middle. The aperture, both in shape and in 

 the form, size, and proportion of its plaits, differs from that of 

 all the species above mentioned. The umbilicus is moderately 

 large and infundibuliform. 



A unique example of this fine new Pupa, with the remains 

 of its animal still present in the aperture, was detected by T. 

 Vernon Wollaston, Esq., the well-known explorer of the Atlantic 

 insect fauna, and author of ' Insecta Maderensia,' ' Canariensia,' 

 &c., in a box containing a number of specimens of P. concinna 

 Lowe, sent to him from Madeira, about a year ago, by the Baron 

 do Castello de Paiva, and marked " Rib. do Inferno.^' Though 

 some doubt therefore must necessarily attach to the precise 

 habitat of this particular single specimen, there can be no ques- 

 tion whatever, with any one whose eye has become at all versed 

 in the aspect of Madeiran Pupa, as to its having been really 

 collected in the north of the island, and probably in one of the 

 few haunts of P. concinna — namely, at the head of the Rib. de 

 Joao Delgado (not far remote from that of the Rib. do Inferno) 

 or of the Boa Ventura on the north side of the Pico Casado, at 

 a considerable elevation. 



This discovery is therefore a fresh instance of the great obli- 

 gations of naturalists to the indefatigable exertions of the Baron 

 do Castello de Paiva, who, though unhappily precluded by ill 

 health from prosecuting his botanical and zoological researches 

 personally, is yet contributing continually, by his employment 

 or encouragement of others, some new acquisition of interest or 

 importance to the domains of what is now termed, euphemistically, 



XVIII. — Remarks on the History o/Dreissena polymorpha. 

 By Dr. Otto A. L. Morch. 



In a review of ^The Record of Zoological Literature' (Ann. & 

 Mag. N. Hist. Dec. 1866, p. 494) an extract is given from a 

 critique of Dr. E. von Martens, to the effect that my opinion as 

 to the identity of Pinna fluviatilis, Sander, with Dreissena poly- 

 morpha depends on an analysis of Sander's account and on "the 

 analogous fact that the occurrence of the genus Unio in Den- 

 mark remained unknown to so careful an observer as 0. F. 

 MuUer." 



This is a mistake. I rely mainly on the facts that Sander refers 

 his shell to the genus Pinna, and that he expressly states that 

 his shell is not figured in Schroter's work on freshwater shells, 



