Chap. IV. 



THE PENNARID^. 



2V9 



described genera also belong. This Hydroid may be very readily recognized by 

 its remarkable, feather-like form (PI. XV. Figs. 1 and V'). The main stem {Firj. 1, 

 a) rises from its stoloniferous basis with a long and gentle curve {Fig. 1"), which 

 extends to its extreme, free end ; it does not, however, trend strictly in the plane 

 of the general curve, which it simulates, but follows it in a slightly transversely 

 zigzag course, giving off a branch at every bend. Obliquely transverse to the 

 plane of this curve, the branches (e) arise, alternately on each side, at regular 

 intervals of about one twelfth of an inch, and bend in curves similar to that of 

 the main stem, but more abrupt, and uniformly in the same plane. The angle at 

 which these branches project from the main stem has a twofold relation ; it sub- 

 tends about fifty degrees from the main stem, on the convex side of its curve, 

 and about forty-five degrees from the plane of this curve. Both the main stem 

 and its branches taper gradually fi'om base to apex. At regular intervals, of one 

 twelfth of an inch, on the convex side of the branches {Fig. 2, a to a^), and in 

 one series, arise the peduncles («*) of the individual hydras (C D E F G). Unlike 

 the main stem and branches, each peduncle, being about one twelfth of an inch 

 long, expands gradually, from the base upwards, and bears on its broadened extremity 

 a single Tubularia-like hydra, each one of which, going from the base of the 

 branch toward the tip, is successively smaller than the preceding (G T ED C). 

 The tip (rt^) of the branch also expands, like the jjeduncles, and bears a single 

 hydra (B), which is much larger than any of those on the peduncles. The same 

 feature is very prominent at the extremity of the main stem {Fig. 1, d). By these 

 characters the genus Pennaria may be distinguished from all others at a glance. 

 It remains now to describe each feature in detail, so far as we may be prepared 

 to do SO; by a few hours study of the living animals, and by the examination of 



Sertularia pennaria, Cavolini, Mem. Polypi Marini, 



1785, p. 134, PI. V. Fiffs. 1-6. 



" " Cavolini, Transl.Sprengel, 1813, 



p. 61, PI. V. Fiffs. 1-6. 

 « " ? Linnteus, Syst. Nat, 1767, 12th 



ed., Tom. 1, p. 1313, No. 26. 

 « " Gmelin, Lin. Syst. Nat., 1788, 



p. 3856, No. 26. 

 " " Oken, Allgemeine Naturg., Bd. 



v., 1835, p. 77. 

 « " Bosc, Hist, des Vers, 1830, 



2d ed., Vol. III. p. 119. 

 ? Aglaophenia, Lamour., Bulletin Soc. Phil., Paris, 

 1812, p. 184. 



? Aglaophenia, Lamour., Hist. Polyp. Flexibles, 1816, 



p. 167. 

 Plumularia, Blainville, Diet. Sc. Nat., 1830, Vol. 

 LX. p. 442.— Manuel Actin., 1834, 

 p. 477. 

 Glohiceps, Ayres, Proc. Boston Soc. Nat. Hist., 1852, 

 IV. p. 193. Name preoccupied, for an 

 Hemipterous Insect, by Lepelletier and 

 Serville, Encyc. Method., X., 1825. 

 Eucoryne, Leidy, Jour. Acad. Nat. Sc, Pliiladelphia, 

 1855, Vol. III. PI. X. Figs. 1-5. 

 Name preoccupied, for a Coleopterous 

 Insect, by Schonherr, Disposit. Method., 

 1826. 



