o06 J. H. ASHWOBTH. 



tcnial opening of nepliridium, Notm. Notopodium. Not. S. Notopodial 

 seise. N/iA. Nepliridium. Nph. Neplirostome. N. Tent. Nerve to pro- 

 stomial tentacle. Nuc. Gr. Nuchal groove. Nuc. Retr. Retractor muscle of 

 nuchal organ. CE. CEsophagus. (E. Gl. ffi^ophageal glands or pouches. 

 Per. Peristomium. Fh. Pharynx. Post. Cr. Posterior cornu of brain. 

 Frost. Prostomium. Prost. Tent. Proslomial tentacle. R. Rods of lateral 

 sense organ. S. Aff. V. Segmental afferent vessel (from ventral vessel). 

 S. Cap. Capillary seta. S. Eff. V. Segmental efferent vessel (to subintestinai 

 vessel). Sept. Septum. S. Furc. Furcate seta. S. H. Sense hairs. S. 0. 

 Lateral sense organ. S. 0. Retr. Retractor muscle of sense organ. Sp. N. 

 Spinal nerve. Stom. Stomach. Subint. V. Subintestinai vessel (sinus). T. 

 Tail segment. V. Mes. Ventral mesentery (imperfect). F. F. Ventral 

 blood-vessel. /, //, ///, IF . . . LX. Somites beginning with the first 

 chaetigerous. 



PLA.TE 13. 



All figures, except Fig. 13, are drawn from specimens of Scalibregma 

 iuflatum. 



Fig. 1. — The large Norwegian specimen, 56 mm. long, seen from the left 

 side to show the external features, prostomium, parapodia, cirri, setae, gills, 

 segmentation and annulation, the sense organs, etc. The nephridiopores 

 [N. 0.), the first of which opens ou the fourth chatigerous anuulus, are very 

 small, and are not well seen in this drawing (see Fig. 5). There are sixty- 

 one segments in the specimen. X 4^. 



Fig. 2. — Ventral view of a very regular American specimen which, if com- 

 plete, would iiave been about 20 mm. long. The prostomium, peristomium 

 and first seven chaetigerous segments are seen. The mouth {Mo.), bordered 

 by epidermal papillae, and the secondary annulation of the skin are seen. The 

 nerve-cord runs along the middle line of the median depressed area, X 22. 



Fig. 3. — Dorsal view of the anterior end of the same specimen to show the 

 prostomium, nuchal grooves, peristomium, and the first and second chaeti- 

 gerous segments, the latter bearing the first pair of gills. X 22. 



Fig. 4. — The first gill of the specimen drawn in Fig. 1, along with a por- 

 tion of the second chaetigerous and succeeding annuli. Only the dorsal half 

 of the gill is fully drawn; the ventral half is cut down to the bases of the two 

 main branches, x 16. 



Fig. 5. — A portion of the tenth chaetigerous segment of the left side of the 

 same specimen. Note the four annuli, tiie skin of which is subdivided inio 

 squarish elevations, tlie epidermal papillae, the prominent lips of the setal 

 sacs, the sense organ, and the nephridiopore {N. 0.). X 16. 



Fig. 6. — Ventral vievy of the posterior end of a specimen 13 mm. long, 

 showing the pygidium or tail segment {T.), the newly formed body segments 



