POLYCELETA SEDENTARIA OF THE FIRTH OF FORTH. 657 



to be the only important difference between the two). Looking at the in- 

 accuracy of the drawings as compared with var. capensis in Pallas's work, and 

 taking into account the indistinctly double series of teeth shown in figs. 5, 8, 

 and 9 of var. belgica, I think that probably the former view is the most likely 

 to be the correct one. In that case P. auricoma of Muller disappears, and 

 becomes P. belgica of Pallas." How a zoologist, after actually referring to 

 the description and figures given by Muller of Amphitrite auricoma, and to 

 the description and figures of both species given by Malmgren in the 

 Nordiska Hafs-Annulater, could suppose the condition of the comb to be the 

 only important difference between the two species, is perfectly incomprehen- 

 sible. The two distinguishing features of Amphitrite auricoma given by 

 Muller are (1) the curvature of the tube, (2) the serration of the margin of 

 the flattened area behind the palmulse. Malmgren mentions both these 

 characters and figures them, and he examined specimens of both species ; 

 only Malmgren made the two characters generic instead of specific, and 

 calls Muller's species Amphictene auricoma. We can state with certainty 

 that in our specimens the tube is perfectly straight, and the margin of the area 

 behind the palmulae perfectly entire. The presence of two separate combs is 

 a constant character throughout the whole family Amphictenidee. 



Habits. — We obtained this species at low tide at Granton, on the surface 

 of sandy flats. The tubes are often half buried, with the thin end projecting 

 straight or obliquely from the sand. We have also taken it with the dredge. 



Malmgren states there are 17 pairs of fascicles of capillary setae, and 

 13 pairs of uncinigerous pinnulae, beginning at the 4th setigerous somite; 

 but we find the last two pairs of parapodial projections before the "scapha," or 

 abdominal region, are destitute of both capillary setae and uncini; there are 

 thus only 15 pairs of fascicles of setae, and 11 pairs of uncinigerous pinnulae, 

 the latter commencing at the 4th setigerous somite. The first three pairs of 

 fascicles of setae are smaller than those following. In front of the 1st setigerous 

 somite are two pairs of branchiae. The pair of combs, which at first sight seem 

 to belong to the buccal somite, probably really belong morphologically to the 

 1st branchial, of which somite they represent the notopodial setae. The 

 semicircular membrane between the tentacles and the palmulae belongs to the 

 buccal somite, while the tentacles themselves belong to buccal somite and 

 praeoral lobe. That this is the real interpretation of the combs is proved by 

 comparison with Ampharete ; in that genus the branchial somite, which follows 

 the buccal, bears ventral to the branchia a dorsal fascicle of setae, specialised 

 into a palmula, and there can be little doubt that it is simply the great develop- 

 ment of this palmula of the 1st post-buccal somite which has produced the 

 condition seen in Pectinaria, and in the other genera of the Amphictenidae. 



The " scapha " represents the reduced abdominal region, and commences at 



