184 OEIGrN-AL ARTICLES. 



latter pass in front of the fibrous septvim above mentioned, and run 

 down, one on each side of the commencement of the Q3So])hagiis, 

 being joined, doubtless, by the veins from the head, and fall into 

 the heart side by side. 



The heart is veiy perfectly supplied with valves. Wellenbergh 

 has described those of the bulbus arteriosus, viz., four in niunber, 

 two of them large, and two small ones intercalated between them ; 

 and also the four semilunar valves which prevent regurgitation into the 

 auricle. The latter he describes as equal : in my specimen there 

 are two of them large, and the intervening ones not half the size. 

 Besides these there are other three semilunar valves guarding the 

 openings of the veins into the aiu-icle, and joined edge to edge Avith 

 one another, viz., one for each hepatic vein, and a very large and 

 muscular one over the entrance of the two systemic veins. 



Branchial cavity. — The gills on each side are enclosed in a large 

 pouch, opening on the outside by an opercular ajoertui-e only two 

 inches long; and internally by five apertures about the same length, 

 of which the first is in front of the first branchial arch, and the last 

 between the fourth branchial arch and the pharyngeal bone. The pouch 

 extends down to the middle line, and upwards almost to the ver- 

 tebral column, and is surrounded almost comj)letely by strong 

 muscles. 



From the preceding sketch of the anatomy of the sun-fish, it 

 will be observed that the leading characteristic of its structiu'e is 

 concentration. Thus the head and shoulders are greatly developed, 

 while the trunk is cut short : of lateral fins it has only one pair, the 

 pectorals : of the mesial fins it only depends upon two for progression, 

 and each of these is compacted into a single organ. Thus also as 

 regards its nervous system, the origins of its spinal nerves arc acumu- 

 lated behind the brain ; and as regards its organs of sense, the 

 olfiietory organ and the ear are very imperfect, while the eye is 

 extremely large. 



ILLUSTRATIONS. 



Plate V. — Fig. \. View of the skeleton of tlic short snn-fish t-alien from a cast. 

 a, is placed under the first vertebra, the bone in front of which is the basioccipital: 

 h, the cartilage corresponding t(j the extremity of the vertebral colnmn; -while aliovc 

 and l)elow it are arranged the caudal fin rays, each consisting of a cartilage, osseous 

 slip and dermal plate: c, cartilaginous ])illow on which the dorsal fin moves: //, that 

 on which the anal fin moves: e, attrahent muscles of tiie dorsal lin: f, muscles of 

 the o]iposite side of the dorsal fin: g, muscles of the opjwsite side of the anal fin. 



Fig. 2. View of the intestines lying in their natural coils, but divested of tlie 

 covering of peritoneum which encloses them, a, tha stomach: b, the gall-bladder: 

 c, the urinary bladder, partially opened to exhibit the longitudinal slit by which d, 

 the ureter, ojiens into it : e, the ovary. 



Fig. 3. Longitudinal section of a portion of one of the dermal phites which 

 terminate the caudal fin rays. The inferior margin of the figure rejiresents the 

 aspect which is imbedded in the integument, showing the elevations on its surface ; 

 while, toward the left side, is a jiortion of the free margin, with the section carriecl 

 through a .spine ; and at the upper part of the same margin is shown the felted 



