PISCES. 75 



BoNATERRE Enc. Meth., Poiss. PI. 99, fig. 408, Bloch, Schneider Syst. 

 Ichth. Tab. 80 is Aviia lentiylnosa Val. 



The swimming-bladder is cellular and double. There is no gill on the 

 gill-cover. ComiDare H. Franque Diss, inaug. nonnulla ad Amiam calvam 

 L. accuratius cognoscendam, Berolini, 1847, under the direction of J. 

 Mueller, with figure of the skeleton, the brain, the heart, and the viscera. 



B. Arterial bulb elastic, with two valves at the base. (Comp. 

 above, p. 60.) 



Section IV. Osteopterygii. 



Fins supported by osseous rays. Skeleton osseous. Dorsal 

 column composed of distinct vertebra. Branchias free. (Optic 

 nerves decussating or placed cross-wise with respect to each other.) 



Oedee VII. Loi^liobrancliii Cuv. 



Branchial laminae broad, clavate, not numerous, arranged in a 

 double row along the branchial arches, folded transversely. Bran- 

 chial aperture small, superior, with a large operculum fixed to the 

 skin throughout nearly its entire circumference. Bays of branchio- 

 stegous membrane small, very thin. Body loricate, angular. 



Cluster-gilled. The singular structure of the gills was first, as it 

 seems, remarked by Tiedemann (Meckel's Archivfur die Physiol. 

 II. 1816, s. 110 — 112, Tab. 11. fig. 7, 8), but more accurately inves- 

 tigated by Rathke {Ueber den Kiemenapparat, s. 50, 51, Tab. iv. 

 fig. 2) and by Eetzius. The deviation from the usual structure of 

 gills is, according to these researches, rather ajjparent than essential. 

 Rathke denies gill-rays to these fishes, which however, according to 

 my observations, is incorrect. 



All the species belonging to this order are of small size; only 

 a few grow to the length of V. — In the sea-horse {Syngnathus 

 hippocampus L.), a species of this order, a hybernation has been 

 observed, during which the respiration is diminished ; see RuscoNi 

 in Meckel's Archivf. d. Physiol, v. s. 268 — 270. 



The eggs are carried imder the abdomen or at the base of the 

 tail, mostly under two longitudinal folds of skin which close like 

 folcUng doors, and in fact, as Eckstroem and other Northern writers 

 have observed, by the male, to whose protection the female consigns 

 them, and with whom the young ones, when born, continue to live 

 for a time. Die Fische in den Scheeren von Morkb, besch'iehen von 



