34(5 Pi'"/- Owens Description of the Lepidosircn anncctens. 



and third branchial arches; and the corresponding arterial trnnks* nndergo 

 no snbdi vision as they wind ronnd tlieni, bnt are continned entire, as in tlie 

 Ainphiuma and Menoponia, to their termination at the opposite side of the vas- 

 cular circle. The brandies which afterwards unite to foi-m the single pulmo- 

 nary artery on each side are given off from near the terniination of the se- 

 cond and third pairs of the primitive aortic trunk ; which thus combine the 

 functions of both systemic and pulmonary arteries. 



The branchiee of the Lepidos'iren resendjle in form those of the Siren, con- 

 sisting of separate elongated filaments, attached only by one extremity to the 

 branchial arch ; but these extremities are fixed directly to the branchial arch, 

 and not to a common pedicle extended therefrom, as in the Siren. Viewed 

 with a moderate lens the tripinnatifid structure is beantifuliy seen in each 

 branchial filament. The first gillf consists of a single row of fourteen of these 

 subcompressed filaments, each of wliich is about one line in length and a 

 third of a line in breadth. The second gill]:, which is developed, as before 

 stated, on the fourth branchial arch, is tiic largest, and consists of a double 

 row of fifteen branchial filaments. The third gill§ has a similar structure. 

 The fourth gill || consists, like the first, of a single row of fourteen trijjinnatifiil 

 filaments, which are shorter and smaller than those of the first. 



The cartilaginous branchial arches are developed on each side in the sub- 

 mucous tissne, and, as before stated, are not attached either to the hyoid ap- 

 paratus below, or to the cranium above. The membrane covering the 3rd, 

 1th, and 5th arches is minutely papillose. The first branchial aperture or 

 interspace^ is a narrow slit three lines long, and is defended by a series of 

 minute denticulations projecting from the branchial arch. Bristles are repre- 

 sented as passing through the five branchial interspaces in Tab. XXV. fig. 3. 

 The second aperture** is the widest; it is five lines long, and its margins are 

 smooth: the third aperture is also five lines long, but is narrower than the 

 second: small cartilaginous teeth are developed from each of its margins, as 

 in the first gill-aperture: the fourth and fifth apertures present the same 

 structure but diminish in size. 



Thus the branchial current, which flows through the interspaces of those 



* Tab. XXVI. fig. 2, i & ;3. t lb. fig. '2, 1. J lb. fig. 2, 4. ' § lb. fig. 2, 5. 



II lb. fig. 2,6. ^ lb. fig. 1, 1. ** lb. fig. 1, 2. 



