ORDER X. 
DERMOPTERI. 
The body is vermiform or worm-like to such a striking extent that Linnaeus himself got de¬ 
ceived, placing one of the species in the class of worms. This external resemblance to worms 
is rendered the more deceiving as the lateral fins (pectorals and ventrals) are altogether wanting, 
the skin naked or scaleless, either verticillated or annulated. The vertical fins themselves are 
reduced to a mucous fold of the derm or skin, which is moreover mucous throughout. The 
internal skeleton being unossified, without distinct vertebrae, instead of which a central carti¬ 
laginous cord, and the head so much blended with the body that in various cases it is not easily 
distinguishable. The pancreas and air bladder, both, are absent. The intestine is straight, 
without either fold or appendages. 
Syn. — Dermopteri, Owen, Lect. Comp. Anat. Vertebr. anim. 1846, 47.—Bd. Iconogr. Encycl. II, 1850, 203. 
Chondrichtlies trematopnes, Dum. Ichthyol. analyt. 1856, 104. 
The Dermopterians subdivide into two sub-orders ; the Pharyngobranchii sen Cirrhostomi 
and the Marsipobranchii sen Gyclostomi. 
The Cirrhostomians constitute but one family, that of Amphioxidae (Lancelet), which has 
no representatives in North America. 
SUB-ORDER. 
MARSIPOBRANCHII s. GYCLOSTOMI. 
The heart is extant, but the accessory arterial heart, known as the bulbus arteriosus , is wanting. 
The truncus arteriosus consists merely of the ordinary membranes which enter into the structure 
of the arteries. The gills are fixed, inclosed within cavities either simple or multipartite, 
receiving the respiratory streams through apertures usually numerous and lateral. 
Syn. — Marsipobranchii, Bonap. Syn. Vert. Syst. 1837, 43. 
Marsipobranchii s. Cyclostomi, Mull, in Weigm. Archiv fur Naturg. 1845, I, 137.— Owen, Lect. Comp. Anat. 
Vertebr. anim. 1846, 48. 
Exotremes .— Dum. Ichthyol. analyt. 1856, 110. 
The Cyclostomians constitute two families; that of Myxinidae (Myxine, Hag, or Borer), 
which is represented in the ichthyic fauna of North^ America, and that of the Lampreys, 
which follows. 
Family PETROMYZONTIDAE, Owen. 
The general form of the body is elongated, cylindrical, or sub-cylindrical, eel-shaped. The 
dorsal, caudal, and anal fins are continuous ; the gills fixed or immovable, and situated in a 
sort of chest. There are seven lateral branchial openings on either side, admitting the water 
to bathe the gills. A single spiracle situated on the upper surface of the head. 
