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652 R. C. PUNNETT.Collar. The musculature of the collar, like that of the proboscis, is somewhat feeblydeveloped. The cavity in the anterior part of the collar is very spacious. The intra-coUarlumen of the oesophagus is unusually large (PI. XLV. fig. 42). The dorsal collar septumis present as usual behind the first root. The ventral septum may be found at the hindend of the collar or it may be absent.Table 4.Pt. flava, var. gracilis.No. of specimen(1)(2)(3)(i)(5)Proboscis coelomFairly largeNot largeas (2)Spaciousas(l)Collar coelomSpaciousas(l)as (1)as(l)as(l)Ventral proboscis .septumNearly to tipof stomochordas (1)as (1)as(l)as (1)Dorso-ventral proboscis musclesPresentas (1)as(l)Dorsal collar septumComplete after1st rootas (1)as (1)as(l)as(l)Ventral collar septumTraces onlyas (1)Absentas (3)Complete athind end ofcollarRacemose ora;anWell markedbut small andunlobulatedWell marked.UnlobulatedWell marked.Slightlylobuhitedas(l)as (1)Dorsal proboscis muscle decussationFairly wellmarked. Noventral circularmusclesNot verymarked. Noventral circularmusclesWell marked.No ventral circularmusclesVery feeble.No ventral circularmusclesas(l)Dorsal roots*RRRRrRRRRRrRRrProboscis pores*1RLrIRIRL onlyNerve cordLength of post-branchial groove-Length of branchial regionLumen continuous•11as(l)•11as(l)•10as (1)•16as (1)•15Length of cornua x 100Length of collar17-419^0\vz14^1Circumference of branchialCircumference of asoph.ces.oes.1-26M41-00•60•85SynapticulaNot more than9Not more than7Not more than7Not more than7The collar cord exhibits a continuous lumen throughout. Three roots are usually tobe found. The cornua of the nuchal skeleton are rather shorter than usual, extending overabout I—i of the collar length.• See foot-note on p. 645.