FISSIPAROUS SPECIES OF TUBICOLAR ANNELID 34I 



is inexpedient to create new sectional terms ; but until a more 

 extended and careful examination of the tubicolar annelides shall 

 have been made with reference to these very points, I do not think it 

 is worth while even to found a new genus for the form I am about 

 to describe, as it possesses all the essential characters of Protula. 

 Specifically, however, it appears to be distinct from all forms of 

 Protula hitherto described, and I therefore propose to call it Protula 

 Dysteri, after my friend Mr. Dyster of Tenby, in whose society it was 

 discovered, and from whom I hope some day to see good work in this 

 branch of science. 



I have already described the vermidom of this species, and I now 

 therefore pass to the details of the organization of the animal itself 

 Protula Dysteri (fig. 3) possesses a very elongated body, which may be 

 conveniently divided into a cephalic, a thoracic, an abdominal, and a 

 caudal portion. 



The cephalic portion (fig. 3, e) can hardly be said to constitute a 

 distinct head, for the oral aperture, which is wide and funnel-shaped, 

 is terminal. The dorsal margin of the oral aperture is formed by a 

 prominent rounded lobe, beneath which are two richly-ciliated, short 

 filaments, which adhere to the base of the branchial plumes, and might 

 be regarded either as their lowest pinnules, or perhaps, more properly, 

 as tentacles analogous to the operculigerous tentacles of the Serpulse. 

 On the ventral side the margin is deeply incised, so that a rounded 

 fissure, bounded by two lips, lies beneath and leads into the oral 

 cavity. From each side of the head springs a distinct branchial 

 plume, whose peduncle immediately divides into four branches. 

 These are beset with a double series of short filiform pinnules, the 

 origins of each series alternating with those of the other. The 

 termination of each branch is somewhat clavate, and when expanded 

 the eight branches are usually gracefully incurved towards one 

 another, the whole having not a little the aspect of a Comatula.i 



The thoracic portion of the body (fig. 3, £? /) is short, but wide 

 and somewhat flattened. It is produced laterally into nine pairs of 

 close-set, double pedal processes. The lower portion of each process 

 forms a mere transverse ridge, beset with the peculiar hooks to be 

 described by and by ; the upper process, on the other hand, is conical, 

 and is provided with elongated setse. The most striking feature of 

 the thorax, however, consists in the peculiar membranous expansion, 

 {J}) which, arising as a ridge upon each side of what might be termed 

 the nuchal surface of the animal, and attached to the sides of the thorax, 



' It is worthy of note, 'how very crinoid the branchial plumes would be if their skeleton 

 were calcified instead of simply cartilaginous, ■ 



