1905.] NATURAL SCIENCES OF PHILADELPHIA. 849 



Amphicteis alaskensis is easily distinguished from the species recorded 

 in my paper of Japanese Polychseta, under the name of A. japonica Mc- 

 intosh, by the character of the paleoh, which in the latter species are 

 only ten or twelve, and when perfect have slender curved tips reaching 

 far beyond the end of the prostomium. 



Amphicteis glabra sp. nov. (Plate XLIV, figs. 5 to 8.) 



The two known examples of this species are of moderate size, the 

 type having a length of 23 mm., of which 15 mm. belong to the thorax, 

 which is 3 mm. wide. 



The form is rather slender, slightly clavate, and gently tapered. 

 There are 20 thoracic segments, 17 of which are setigerous, and 15 ab- 

 dominal segments, or possibly more as the extreme posterior end is 

 macerated. 



The entire prostomial region is relatively much broader than in A. 

 alaskensis and its median plate (fig. 5) much wider than long, irreg- 

 ularly pentagonal, with the long anterior border cleft into a pair of 

 short divergent lobes, from between which a broad median groove ex- 

 tends about halfway across the dorsal surface. On each side of this plate 

 is a small triangular area, which is again bounded laterally by a narrow 

 fold ending freely in front. The pigmented transverse ridges occur as in 

 A. alaskensis, but are longer correspondingly to the width of the prosto- 

 mium, which they cross nearly transversely; beginning at the posterior 

 end of the lateral fold mentioned above they arch forward and meet 

 at a wide angle in the median line immediately behind the apex of the 

 cephalic plate. The entire dorsal surface of the prostomium lies in 

 nearly the same plane, and its anterior portion is not bent downward at 

 an angle with the rest as in A. alaskensis. The tentacular membrane is 

 rather low and has a nearly regular elliptical outline, and the few ten- 

 tacles remaining are scarcely longer than the entire prostomium. 



The upper lip is slightly cleft medially and the peristomium in the 

 region of the lower lip is enlarged and more or less tumid. Ventrally 

 somite II is about one-third as long as the prostomium, and dorsally it 

 exhibits a transversely elongated median area slightly elevated above 

 and separated from the surrounding parts by a slight groove. Somite 

 III is nearly as long as I ventrally; dorso-laterally it is prominently 

 enlarged to bear the paleoli, and dorsally becomes very much reduced 

 in length to form a narrow border that passes along the anterior margin 

 of the branchiferous area and joins the median interbranchial area of 

 IV. Succeeding somites are well differentiated and of nearly equal 

 length throughout the thoracic region. The dorsal portion includes 

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