202 Dr. C. Collingwood on Nudibranchiate Mollusca. 
same spot at intervals of three and five years, and at last in 
company with its congener, exhibiting the curious and interest- 
ing spectacle of a small rock-pool containing an entire genus, 
the species of which are—one a widely-distributed animal, whose 
geographical range extends from there to the Mediterranean 
Sea, the other apparently one of the most localized animals 
upon the face of the earth. 
The value of local lists is now fully recognized ; and although 
they can never be deemed perfect, inasmuch as enlarged research 
and process of time may always be expected to bring to light 
additional species, nevertheless the collection of such carefully 
prepared lists is undoubtedly the best means of illustrating the 
Fauna of a country, as well as of elucidating the geographical 
range and distribution of animals. The followmg Catalogue of 
the Nudibranchiate Mollusca of the Mersey and Dee may be 
regarded as accurate and complete up to the present time. 
Catalogue of the Nudibranchiata of the Mersey and Dee. 
. Doris tuberculata. Mersey and Dee; common. 
—— Johnstoni. Mersey and Dee; once or twice. 
proxima. Mersey and Dee; common (found nowhere else). 
—— bilamellata. Mersey and Dee; abundant. 
—— pilosa. Mersey and Dee; not uncommon. 
—— subquadrata. Dee; once (the second known specimen). 
—- depressa. Dee; once. 
. Polycera Lessonit. Between Mersey and Dee; once. 
ocellata. Mersey and Dee; occasional. 
10. Ancula cristata. Mersey and Dee ; common. 
11. Tritonia Hombergit. Mersey and Dee; occasional. 
12. —— plebeia. Mersey and Dee; occasional. 
13. Dendronotus arborescens. Mersey and Dee; common. 
14. Doto coronata. Mersey and Dee; very common. 
15. Eolis papillosa, Mersey and Dee; common. 
OWS OR to 
16. coronata. Mersey and Dee; common. 
17. —— Drummondi. Mersey and Dee; very common. 
18. —— rufibranchialis. Mersey and Dee; not uncommon. 
19. —— Landsburgii. Mersey and Dee; rare. 
20, -—— concinna. Mersey; common (the second known locality). 
21. —— olivacea. Dee; once taken. 
922 aurantiaca. Mersey and Dee; common. 
23. —— picta. Mersey and Dee; not uncommon. 
24 exigua. Mersey; apparently rare. 
25. —— despecta. Mersey; common. 
26. Embletonia pallida. Mersey (the only known locality); very rare. 
27. Antiopa cristata. Dee; occasional. 
28. Antiopa hyalina. Dee (the only known locality); very rare. 
15 Oxford St., Liverpool, 
August 1860. 
