ON BRITISH MARINE ZOOLOGY. 941 
Record of Classes and Tribes partially observed. 
The enumeration of species in each dredging paper is complete so far as 
the Testaceous Mollusca are concerned, and usually, also, the Echinodermata. 
Other tribes of animals, as well as plants, in consequence, in most cases, of the 
impossibility of determining all the species at the time, and partly from the 
great amount of labour required to register completely the tribes above 
noted, did not receive the same degree of attention. In most instances they 
were, however, carefully collected ; and in the works of Bell and Johnston 
especially, many records of depths and localities will be found which were 
derived from specimens collected and transmitted to those eminent naturalists 
during the course of these researches. In the majority of the dredging 
papers, there are, however, memoranda of various extent, noting the more 
remarkable instances of every tribe found, and often their comparative 
abundance. ‘These 1 shall now proceed to abstract. 
Mollusca Nudibranchiata. 
The small number of these beautiful creatures recorded in the dredging 
papers is not to be attributed to their having been unobserved, but rather 
to their absence from the ground usually examined. The majority of species 
inhabited the shallower parts of the Laminarian zone, and very numerous 
forms are littoral—hence living without the region assigned for this inquiry. 
In the magnificent work of Alder and Hancock on the British Nudibranchia, 
published by the Ray Society, the distribution and localities of this tribe have 
been most carefully attended to. 
Those noted in the papers are,— 
Melibeea coronata, Dorset, in 15-20 f. s. gr. 
fragilis, Isle of Man, 20-25 sh. Cornwall, 25 sh.s. Dorset, 
20-25 s. 
Tritonia, sp., Dorset, in 15-20 gr. 
--- Hombergi, Isle of Man, in 25 sh. 
plebeia, Isle of Man, in 28 sh. 
Flolidia, Isle of Man, in 18-25 f. Clyde, in 20 f. Zetland, in 7 f. 
Polycera, Hebrides, in 4-5 f. 
Idalia, Zetland, in 35 f. 5. 
Mollusca Cephalopoda. 
Cephalopods are difficult to take with the dredge on account of the 
rapidity of their motions. The following instances are recorded :— 
Sepiola, 15-20 f. gr. and 40 m. Hebrides; and its spawn, in 285 5. s. 
Cornwall. 
Octopus, 30 f. gr. Hebrides, and 25 f. sh. Isle of Man. 
Mollusca Ascidia. 
These are rarely recorded in detail, because the difficulty of determining 
the species in the present state of our knowledge of the tribe is very great. 
Such records however as are given are important :— 
Cynthia microcosmus is recorded from 10 f. 5. m. and 25 f. st. s. in 
the Hebrides. 
—— echinata, from 50 f. m. in the Hebrides, and 80 f. sand in Zet- 
land, where it also occurs among weed in 7 f. 
—-—, a new species from 30 f. gr. Croulin Island. 
—— aggregata, from 7-12 f. st. gr. Dartmouth. 
_—— tessellata and morus, Devon, in 20-25 f. Localities for other 
members of this genus may be found in the ‘ British Mollusca,’ 
vol, i. part 1 and 2. 
1850. R 
on; 
