LAND AND FRESH WATER MOLLUSCA OF THE EAST RIDING. 1 67 



Unio tumidus Phil. 



The occurence of this species in Holderness requires 

 confirmation. 



Derwentland. — York, " Musculus angustior " (List. Hist. Animal Angl. 

 p. 149, tab. 2, f. 30 ; Appendix p. 12, tab. 1, f. 6), " In fluvio Ouse 

 juxta Eboracum copiose "; " found with piciorum in Ouse in Yorks." 

 (Pennant Brit. Zool. 1812, vol. 4, p. 162); (Maton and Rackett, quoting 

 Lister ; Hincks, Ann. Nat. Hist. ser. 1, vol. 5, p. 367; S.W.N.) ; in 

 the Ouse but very rare ; var. radiata occurs amongst the rest 

 (R.M.C.). Market Weighton canal between Newport and Cliff 

 (J.D.B. circular 75 ; H. F. Parsons, Nat. 4, 90). 



Holderness.— R. Hull (J.D.B., Nat. 8, p. 185). Sutton drain, between 

 Wawne Road and the Great Culvert, in mud thrown out when 

 cleaning (J.W. B. ). 



Unio pictorum (Linn.). 



Not in the Census. As in the case of the last species, it 

 is uncertain whether its range at York extends to the East 

 Riding. 



Derwentland. — York, " Musculus angustissimus .... cum superiore, 

 at rarior est " (Lister Hist. Anim. Angl. Appendix p. 13, tab. I, fig. 

 4); "Ouse in Yorks" (Pennant Brit. Zool. 1812, vol.4, P- '62); 

 (Maton and Rackett, Linn. Trans, vol. 8, p. 38 ; T. Brown 

 "Illustrations" 1844, p. 81); common in the Ouse below York 

 (W.C.H.) ; very fine and very abundant in the Ouse but the number 

 below the city far exceeds that above (R.M.C. ). Market Weighton 

 canal between Newport and Cliff (J.D.B. circular 75 ; H. F. 

 Parsons Nat. 4, 90). 



Holderness. — [Canals about Hull, Forbes and Hanley, vol. 2, p. 146.] 

 Leven canal; R. Hull (J.D.B. Nat. 8, p. 185). ["I found this 

 species ( U. rostrata)\x\ the canal near Hull," T. Brown "Illustra- 

 tions," p. 82]. Sutton drain, with U. tumidus as above (J.W. B.). 



Var. curvirostris Norm. : — Ouse below York (W.C.H. J. of C. 3, p. 

 178) ; in the Ouse but not common (R.M.C). 



Var. radiata Moq. : — Pretty common amongst the rest (R.M.C). 



As indicated above, Lister described two species of Unio from the 

 Ouse, Nidd and Foss. Subsequent authors agree in considering 

 these distinct with the exception of Montagu, who however does not 

 refer to the figure or description in the Appendix but appears to have 

 decided from the figures of the Historian Conchyliorum. There is 

 much confusion in the references, e.g., Turton (ed. Gray) refers to 

 tab. 2, f. 30, as Unio pictorum, and Appendix fig. 6 as U. tumidus 

 though the second figure is a copy of the first. Similar mistakes 

 occur in Maton & Rackett (loc. cit.), and Leach (ed. Gray), 

 Molluscorum Britanniae Synopsis. Lister's descriptions and figures 

 are 



