518 ON THE FAUNA AND BOTTOM-DEPOSITS NEAR THE 30-FM. LINE 



the Prawle Stony Ground. The fifth (Sta. 84) was clearly on a fine sand 

 ground with shells, similar to the sand bordering the Eddystoue gravels. 

 Imperfect as the lists doubtless are, one cannot but be struck by the 

 fact that on the whole we are dealing with the same species as those 

 found on the grounds examined during the present investigation, 

 arranged possibly in a somewhat different manner, with a few forms 

 added and a few taken away. 



Some of the more striking differences may be pointed out, in order to 

 indicate the nature of the information which one would wish future 

 investigators to supply when dredging in similar localities. The con- 

 stant abundance of Tubularia indivisa and Tubularia larynx, both on 

 the coarse and fine grounds in these North Sea hauls, is noteworthy. 

 Fragments only of T. indivisa were obtained on the Eddystone to Start 

 Grounds (viz., on the Prawle Stony Ground, attached to a large stone), 

 and so far as our experience goes the species in this neighbourhood 

 is confined to rocky situations. A knowledge of the exact conditions 

 on the North Sea Grounds, and of the kind of material to which the 

 hydroid is generally attached,* might throw light upon this difference. 



Halecium halemium is present and sometimes abundant on each of 

 the coarse North Sea Grounds, whilst it is absent from the sand. This 

 is similar to its distribution on the Eddystone Grounds, but on these 

 latter it is in by far the larger number of cases attached to the tubes of 

 Chaetopterus, a species which is not recorded in the Fommerania reports. 

 Schulze makes the general statement that JI. halecinum was attached to 

 shells, worm tubes, etc., but there is no indication as to whether any 

 particular worm takes the place which Chaetopterus occupies on the 

 Eddystone Grounds. 



Amongst the Crustacea one may notice that in the North Sea hauls 

 Stenorhynchus rostratus { = S. phalangium) takes the place of S. longi- 

 rostris, and that, as on the Eddystone Grounds, Stenorhynchus and 

 Inachus are present on the fine grounds, but rare or absent on the 

 coarse. 



The almost entire absence of Pecten opercularis and the entire absence 

 of P. maxivius on these particular North Sea Grounds is noteworthy, 

 and there is no species which obviously takes the place which they 

 occupy on the corresponding Eddystone Grounds. On the other hand 

 Fusus antiqmcs on the North Sea Grounds seems to take the place of 

 Buccinum undatum on the Eddystone Grounds. A similar change of a 

 striking nature (confirmed by other hauls of the Ponimerania) is the fact 

 that Fiustra foliacea seems to exactly take the place usually occupied by 

 Cellaria Jistidosa and sinuosa in the neighbourhood of Plymouth. 



* T. larynx is stated by Scliulzc to be attcaclied to shells and to other hydroids, e.g., 

 Tubularia indivisa. No statemeut is made as to tlie attachnieut of the latter s])ecies. 



