Reprodnctive Organs of Spams Centrodontus. 31 



from a single iiiterspinoiis bone respectively. The last two ra^ys are 

 close together at their bases. Sometimes all the spines of this fin are 

 covered with thick skin. The angle between the last ray and the 

 ventral edge of the body is filled with a little membrane ; it is usually 

 not so large as the membrane at the end of the dorsal fin. 



Pectoral Fin. — The pectoral fin furnishes an important specific 

 character. Its lo^^■er rays are thick and fleshy, and separated from 

 one another in a considerable 2:)roportion of their length. The upper 

 part of the fin contains thin ra3's which have each from one to four 

 points. This part of the fin is cut square across. The total number 

 of raj^s was 19 (11 thin and 8 flesh}') in seven fishes, and 20 (11 thin 

 and 9 fleshy) in three fishes. Of the thin ra3"S the first and second 

 had single tips ; the third to tenth Avere split into more than t\\'o 

 tips ; the eleventh va.y was either single or sjalit into two at the tip. 

 The fleshy rays are single. The fleshy rays are separated from each 

 other in from one-third to one-half their length. The}^ were 

 often damaged. Sometimes certain of the rays were fixed bent at a 

 sharp angle, as if they had been broken across and had healed in the 

 bent condition. They may be damaged on one side of the fish and 

 normal on the other side. In one fish several of the flesh}' rays had 

 been cut oflTon both sides. 



The longest ray in the fin is sometimes one of the last thin rays, 

 but in other cases it may be one of the first fleshy rays, e.g., the 14th ray. 



The axilla of the pectoral fin is deep, and there is much slack skin in it. 



Ventral Fin. — The number of vajs in this fin ^^'as counted in six 

 fishes. No variation was found, the number being one spine-ray and 

 five soft rays. There is a broad membrane binding the last ray to the 

 ventral surface of the body (»)/*., Fig. 100). The spine-ray is entirely 

 covered with thick skin. 



Caudal Fin. — Twenty-four ra5^s were counted in the case of one 

 fish. The dorsal and ventral edges of the base of the tail form some- 

 what sharp ridges. The top and bottom edges of the fin are often a 

 little irregular, as if the rays had been shorn. The lowest three or 

 four rays are sometimes of a thicker form than the other rays. The 

 liind margin of the fin is either straight across or slightl}^ concave. 



Veriebrce. — In 12 fishes the number of vertebras was not found to 

 vary. Twenty-five were found in each case. The first haemal arch 

 was in twelve cases on the seventh vertebra ; the fii'st hjemal spine 

 was in three cases on the eighth ; the tip of the haemal spine 

 was forked in one case. The end of the first interspinous line of the 

 anal fin met the hsemal spine of the eleventh vertebra in two instances. 



Measurement Characters. 



Certain measurements similar to those made on Sebasfes marinus 

 were recorded for this species. The results have been introduced into 

 the Table on page 18. 



Comparison between Sebastes d/tctijlopterus and Sebasfes marinus. 



In colour they are very similai-, both being red-coloured. The red 

 colouration differs in the two fishes in its shade. 



In side view the two species closely resemble one another. 

 Important differences are also detected. Generally Dactylopterus is 



