TA,KEN i.T ALNJIOUTH, NORTHUMBERLAND. 487 



coming into line with any one of the three divisions established 

 by Thorell. I therefore propose for the reception of Ilyopsyllus 

 a new section under the name Leptostomata. The divisions of 

 Copepoda based upon the structure of the mouth organs would 

 then stand as follows. 



Series 1. Gnathostomata 



Os mandibulis duabus libens tribusque paribus maxillarum 

 instructum, siphone nullo. 

 Series 2. P(ecilostomata 



Os mandibulis et siphone carens, maxillarum paribus 3 — 1 

 ( — 0) instructum. 

 Series 3. Leptoixomata 



Os mandibulis duabus perparvis et maxillarum paribus (?3) 

 tenuissimis instructum, siphone nullo. 

 Series If. Siphokostomata 



Os in siphonem, mandibulis 2 plerumque includentem pro- 

 ductum et maxillarum paribus 3 — instructum. 

 According to the view taken in this arrangement, the differ- 

 ences which separate Series 1 from 2, 3, and 4 are analogous to 

 those which divide mandibulate from haustellate insects, the 

 chief distinction between Siphonostomata and the two inter- 

 mediate groups, Poecilostomata and Leptostomata, being the 

 presence of a siphon or suctorial tube in which certain of the 

 mouth-organs are enclosed. There may, of course, be tran- 

 sitional forms difficult of reference to any group, but this is a 

 disadvantage common to all systems of classification. 



Series Ij.- Siphonostomata. 

 EcHiNOCHERES vioLACEXj:^, Claus. (Plate XII., figs. 9, 10). 

 1889. Echinocheres violaceus, Claus, Uber neue oder wenig 

 bekannte halbparasitische Copepoden, p. 30, 

 Plate VI., figs. 1—10. 

 A single specimen which agrees closely with Dr. Claus' figures 

 and description was found in a gathering taken among Algse in 

 tide-pools. I give a drawing of the entire animal and an en- 

 larged figure of the anterior antenna. My specimen, however, 

 was a little defective as to setse, which had doubtless been 



