176 ALFRED GIBBS BOURNE. 



lucullana, the first rudiments of the branchiae arise as two 

 processes which soon bifurcate, and are clearly placed below 

 the very large prostomium. This is at a stage when three 

 setae bundles are visible. 



The prostomial lobe, which in Dasychone never bears any 

 tentacles or palps, gradually aborts, and the secondary branchial 

 filaments appear to have a terminal origin. Thus develop- 

 mental history, so far as we know it, favours the view of the 

 peristomial nature of the branchiae. 



Systematic Description. 

 Family — SERPULiDiE. Tribe — Sabellidse. 



Haplobranchus, g. n. 



Head distinct. 



Pro- and peristomium almost fused, two prostomial tentacles, 

 two palps. 



Collar slightly developed. 



The paired branchiae consist each of four free tentacles 

 united at the base in pairs, and entirely devoid of secondary 

 filaments ; they are richly ciliated. No blood-vessel in the 

 branchiae, a single blood vessel in each palp. 

 Tubiparous glands not united. 

 Caudal eyes absent. 

 Auditory capsules absent. 

 Sexes distinct. 



H. aestuarinus, sp. n. Isle of Sheppey, England, W. H. 

 ShrubsoU; Mouth of the Lifi'ey, Ireland, Tho. Bolton. 



Specific characters where a single species only is known 

 must always be guardedly put forward, but judging from allied 

 forms, the following would seem to have such weight : 

 Length 4 — 6 mm. 



Nine somites (8 setigerous) in the thorax. 

 Three somites in the abdomen. 

 The shape of the setae, figs. 8 — 14. 

 Blood green. 



