672 PATAGONIAN EXPEDITIONS I ZOOLOGY. 



The small specimen shows immaturity not alone in the condition of the 

 reproductive organs, but in the external annulation. Throughout the 

 middle region of the body the secondary annuli into which ar and aj 

 are divided are imperfectly separated. This is expressed not so much in 

 their relative size, which is scarcely appreciably less than in the mature 

 specimen, but very obviously in the relative shallowness of the furrows 

 bilb2 and b$lb6 as compared with bzla2 or a2lb$. Figure 4 is a careful 

 camera drawing of the ventral surface of this specimen when mounted in 

 glycerine, in which medium the ganglia can be seen quite clearly and are 

 also represented in the figure. Generally the ganglia lie principally 

 within a2 throughout the quinqueannulate region. The subcesophageal 

 complex is in VI and VII and the supracesophageal chiefly in VI. On 

 the dorsal surface the furrow a2\b$ is distinctly deeper than &2la2, result- 

 ing in the natural division of the five annuli into two groups of three and 

 two respectively. 



Alimentary Canal. The upper lip (prostomium) is somewhat wrinkled 

 below, but lacks any definite and distinct median sulcus. The mouth is 

 small in the preserved specimens, scarcely larger than in a nephelid in 

 the larger, but relatively larger in the smaller one. Jaws are absent, 

 though the median dorsal one is probably represented by a small rounded 

 tubercle occupying the corresponding position and surrounded by a shallow 

 trench, immediately laterad to which is a pair of broad, low, longitudinal 

 muscle columns, and again beyond these a similar pair of narrower ones, 

 but no trace of lateral jaws. Muscles and gland ducts enter the dorsal 

 tubercle, but there are no teeth. A low, narrow fold passes between the 

 buccal chamber and pharynx dorsally, but fades out ventrally. 



The pharynx (Plate XLIX, fig. 9) is capacious and extends to the 

 region of the genital pores in the middle of XII. Its inner surface is 

 thrown into slightly marked longitudinal muscular ridges. These begin 

 anteriorly as a dorsal pair and a median ventral one, alternating with 

 three much narrower ones. Each of the larger set almost immediately 

 divides into several, so that for the greater length of the pharynx ten or 

 twelve ridges are recognizable. None of these is strongly marked and the 

 internal surface of the pharynx is nearly smooth and regular, but shows 

 a slight tendency toward a triangular section. 



A stomach of very simple character extends from XIII into XIX, where 

 it passes, without any very sharp demarkation, into the intestine. Seven 



