396 MRS. E. w. SEXTON ON A [Apr. 28, 



divisions of the Amphipocla, the tribe Prostomatm being estabhshed 

 by Boeck for its reception. 



Boeck noted many points of resemblance to the Lysianassidfe — 

 the structure of the upper ;intenn?e, the powerful hand of the first 

 gnathopod, and the slender characteristic second gnathopod ; but 

 it remained for Sars to prove conclusively its relationship to that 

 family, in which it now rests. 



Boeck considered, and Bovallius and Sars are in agreement 

 with his views, that the peculiar tubiform structure of the mouth 

 indicates a parasitic habit. Most of the specimens have been 

 taken on fish. The first were caught by Prof. Rasch by lowering 

 in the trawl a freshly-killed and skinned bird, to the body of which 

 they clung, sucking the Wood. Herr Storm found it in the 

 Throndhjemsfjord "parasite on a shark" {Boeck), as well as on 

 the common black dogfish {Sars). Bovallius captured several 

 specimens in the Hardangersfjord, " pax^asites on or in company 

 with an Asterias." Prof. Sars has taken it in the Throndhjems- 

 fjord, in all cases clinging to the skin of the black dogfish {Spinax 

 niger). Mr. Tattersall's specimen, the only one yet recorded out 

 of Norway, was taken in a small tow-net attached to the trawl. 



The Mediterranean form also has always been recorded as taken 

 on fish. The tirst specimens were found, as Costa states, on 

 "squalo" and " merluzzi " ; the three examined by Delia Valle 

 were taken on " merluzzi," and the one recorded by Brian was 

 discovered in the mouth of a " Chlorophthabmts ayassizi." On 

 the other hand, Chevreux"s specimen from the Bay of Biscay, the 

 ' Huxley ' specimen from the north of the Bay of Biscay, and 

 Mr. Tattersall's six specimens from the West of Ireland, were all 

 fx^ee-swimming. Mr. Stebbing's S. -African species also appears 

 to have been captured free-swimming. 



It would seem better, all things considered, to describe this 

 genus as predatory rather than pai'asitic. All the Lysianassidfe 

 are carnivorous : in many of the genera they move in vast hordes 

 devouring any carrion they find, and not hesitating to attack 

 anything living unable to escape them, such fis fish caught in a 

 net. Many instances of this could be cited ; to take an example 

 from my own observation — in the Nassa-pots placed in Plymouth 

 Sound by the Marine Laboratory I have found the common little 

 Orchomenella nanus swarming in thousands, not only eating the 

 dead crabs used for bait, but devouring the living polyps of the 

 Perigonimus on the Nassa shells, and attacking the Nassa them- 

 selves whenever extruded. And again, in a dredging taken ofl:' 

 the Eddystone, over 18,000 Scopelocheirus hopei were found in two 

 Echinus- shells. A statement of Prof. Delia Valle's supports this 

 view in regard to T. nicceense ; in the 'Fauna' (15), p. 287, he 

 says, referring to his three specimens : — " Uno di questi individui 

 portava ancoia imprigionato nel formidable organo di presa dei 

 suoi gnatopodi posteriori un pezzo di carne del pesce su cui era 

 attaccato." {Cf. also Chevreux, 21.) 



Two featui-es render this genus notew^orthy — the inflation of one 



