PARAONIDAE. 3G1 



The branchiae begin on the sixth somite. The fii-st seven branchiferous 

 somites have each a smgle pair of simple branchia, each of which is inserted on 

 the dorsum nearer to the correspondmg notopodium than to the middorsal line. 

 These branchiae are flattened and are acutely acmiiinate. (Plate 64, fig. 7). 

 Each is purpUsh proximally and less strongly so along each side to near the tip. 

 They increase in length caudad, but in no case when laid transversely do they 

 reach the middorsal Une. The eighth branchiferous somite in both of the type- 

 specimens has a simple branchia on the right side, while that on the left side is 

 double, two equivalent branches arising from an almost obsolete common base. 

 On the ninth and following somites the branchiae each presents two equivalent 

 branches, contiguous or united at the veiy base, as far back as the thirteenth 

 branchiferous sonaite, inclusive, in one specimen and the fifteenth in the other. 

 (Plate 64, fig. 8). In the first case, on the thu-teenth, fourteenth, and fifteenth 

 brancliiferous somites the branchiae have three branches. In the second speci- 

 men, on the last somite of the division (fifteenth branchiferous) the left branchia 

 has three divisions, and the right one foiu*. In the anterior region of the posterior 

 di^dsion of the body the branchiae are much more strongly developed, the num- 

 ber of filaments rising to as many as nine. .\11 the filaments in each lateral 

 group are arranged in a straight transverse series. (Plate 64, fig. 9). The 

 space between the series of opposite sides in aU cases exceeds the length of the 

 series, but the latter is decidedly greater than the distance from the most mesal 

 filament to the middorsal line. The filaments in this region are much longer 

 than in the anterior region. Most filaments are lost; but one at the mesal end 

 of a series was found which reached across to the ectal end of the opposite series. 

 In going farther caudad the number of filaments in each group and their length 

 again decreases. In the most posterior region of the longer type the branchiae 

 have become again all simple, mth a single pair to each somite, these short and 

 without purplish pigment. (Plate 64, fig. 10, 11). 



Locality. Off Panama: Sta. 3354 (lat. 7° 09' 45" N., long. 80° 50' W.). 

 Depth 322 fms. Bottom of green mud. Bottom temp. 4G° F. 23 February, 

 1891. Two specimens. 



Paraonidae. 



Certain genera, namely Aricidia and its allies, that have commonly been 

 placed under the Ariciidae are more properly to be placed in a separate family, 

 as was first pointed out by Mesnil and Caullery (Bull, sclent., 1898, 31, p. 126). 



