484 



ANNELIDA. 



region. Notopodia of the middle region in the form of fins, often lobed. They 

 inhabit U-shaped parchment-like tubes, the two ends of which are placed at 

 some distance from each other, and project above the sand. The skin of the 

 worm is soft and delicate. The larvae are mesotrochal. Telepsainis G. Costa, 

 two long tentacular cirri ; body divided into two regions ; Spiochaetopterus Sars ; 

 Phyllochaetopterus Gr., two pairs of tentacular cirri; body divided into three 

 regions. Chaetopterus Guv. (Fig. 395), two tentacular cirri. Body divided into 

 three regions. Phosphorescent. Ch. variopedatus Ren., Channel Islands, English 

 coast, etc. , anterior region with 9 pairs* of setigerous conical parapodia ; middle 

 region of 5 segments, of which the first carries two large wing-like processes 

 directed forwards (notopodia), the second carries a dorsal and ventral sucker 

 (modified parapodia), the third, fourth, and fifth a membranous fin-like noto- 

 podium the fans, and a ventral bilobed neuropodium ; the posterior region 

 consists of from 25 to 35 less modified, similar segments, with notopodium and 

 bilobed neuropodium. 



Fam. 3. Magelonidae.f Body divisible into two regions by differences in the 

 setae. Prestomium large and flat, two long peristomial cirri. Large eversible 

 bticcal region, blood of madder-pink colour when oxygenated, and colourless 

 when deoxidized (Memerythrin, found also in Sipunculus) ; the colouring matter 

 being contained in globules which float in the colourless plasma ; isolated nuclei 

 are also found in the plasma. Live buried in sand. Sole genus, Magelona 

 F. Miill. 



Fam. 4. The Ammocharidae may be placed here. They live in sandy tubes, 

 and the mouth is surrounded, except ventrally, by a membrane, which is frayed 

 out marginally into filaments, and is probably an appendage of the peristomium. 

 The anterior segments longer than the hinder ones. Sole genus Oivcnia D. Ch. 



Sub-order 3. TEREBELLIFORMIA. 



The prestomium is a more or less prominent lobe (upper lip) with 

 or without tentacles, but without palps. The peristomium may 

 carry cirri or tentacular filaments. The parapodia are feebly de- 

 veloped; there are no ventral cirri; the dorsal cirri may exist and 

 function as gills on some of the segments. The setae are unjointed, 

 and uncini are usually present. The buccal region is not eversiblr, 

 and there are no jaws. The septa are usually incomplete, with the 

 exception of one strongly-developed diaphragm anteriorly. The 

 nephridia are dimorphic, those of the prediaphragmatic segments 

 being of large size and excretory, while the posterior nephridia are 

 mere funnels which serve as generative ducts. They are burrowers 

 or tube-formers, and in the majority the tube-forming glands are 

 grouped on the ventral surface of the anterior segments, where 

 they form gland-shields. 



The number is variable; specimens have been found with 12, or with 9 on 

 one side and 8 on the other. 



t W. B. Benham, Q. J. M. S., 39, 1896, p. 1. 



