AMMOCHARIMh 353 



cephalic and buccal region is shorter, and the collar on the anterior edge of the first 

 bristled segment less developed, though a similar fold occurs on each side at the groove, 

 near the first foot which has a tuft of stout bristles with tapered tips and may have 

 very narrow wings, but in the shorter developing forms these are indistinguishable. 



The typical foot has a tuft of strong capillary bristles, many of which have finely 

 tapered tips with spikes, and beneath the spiked region a very narrow wing as in A. biceps. 

 A tuft of much more slender forms accompanies these, with minutely spiked tips, whilst 

 longer, slender forms, spiked from the tip to a little above the insertion, occur amongst 

 the stronger forms first mentioned. Few of the bristles, however, were entire. A distinct 

 papilla marks each foot anteriorly. 



The hooks (PI. CVIII, fig. 13) are characterised by their bold curvature, the 

 prominent process from which the gular bristles spring, the nature of the interval 

 between the process and the great fang, which makes a little less than a right angle 

 with the neck, and by the presence of five teeth above the main fang. The neck is 

 rather long and constricted above the shoulder, and the gular bristles curve upward to 

 the second tooth on the crown. Compared with a smaller example of Asychis biceps from 

 Norway, the contour of the crown differs, the space between the main fang and the 

 gular bristles is larger, the process giving origin to the bristles larger, and the neck of the 

 hook is longer. These characters are more pronounced in the larger Asychis from Loch 

 Linnhe in which the gular bristles are still closer to the neck and fewer teeth occur above 

 the main fang. In lateral view, of course, all the teeth are not seen. A considerable margin 

 has to be given for variation, but the form procured by the ' Porcupine ' differs from the 

 two mentioned and also from Arwidsson's figure. 



Family XXV. — AMMOCHARiDiE, Malmgren, 1867. 



Cephalic lobe confluent with the buccal, variable or with a series of branched (peri- 

 stomial P) branchiae. Buccal segment devoid of bristles. Body somewhat short, rounded, 

 slightly attenuate posteriorly, segments few, anterior longer than broad, posterior decreased 

 in length, bristled. Posterior end variable. Intestine straight. Dorsal bristles capillary, 

 in slender fascicles ; ventral, numerous, minute, unciform, with curved tips, shaft straight, 

 arranged in transverse rows. Tubicolar; tubes flexible, covered with grains of sand and 

 fragments of shell, and immersed in sand. 



In the structure of the body- wall this species offers certain important features, since 

 the central nervous system is situated in the hypoderm, which is well-developed through- 

 out, but as a special account will elsewhere 1 appear, it has been thought unnecessary to go 

 into detail. The absence of oblique muscles, and the special glandular organs are note- 

 worthy points. 



Claparede, who states that the cuticle 2 in this form is tough, observes that the vascular 

 plexus on the intestine resembles that in the Serpulidae. In the mid-region is a large 



1 Festschrift for Professor Ehlers of Grottingen, 1915; but the war may necessitate a different 

 publication. 



3 Other authors describe the cuticle as occurring only anteriorly, the epiderm alone being present 

 posteriorly. 



168 



