122 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



Anal fin. — A finfold was present at 2.6 mm., 

 and a full complement of rays was seen at 4.4 mm. 

 (pro-spines and pro-soft-rays distinguishable). 

 The first ossified rays were seen in stained speci- 

 mens at 3.5 mm.; and ossification proceeded 

 posteriorly. Segmentation of pro-soft-rays was 

 first seen at 5.3 mm., and was complete by about 

 8.2 mm. There was no branching of anal rays 

 in a 13.9-mm. individual, but branching had be- 

 gun with the most posterior rays at 15.0 mm., 

 and was complete by 16.8 mm. 



The full complement of anal spines, three 

 (III), found in all 233 prejuvenile, juvenile, and 

 adult specimens so e.xamined, was present by 

 8.2 mm., when segmentation of the soft-rays 

 was complete. Variation in the numbers of 

 fully developed soft-rays is shown in table 4. 

 The anal fins of individuals with a dorsal count 

 other than the modal X, 11 show the modal anal 

 ray count of TTI, 10 in all but one instance (a 

 specimen with a dorsal-ray count of X, 12 and 

 an anal-ray count of III, 11). 



Pelvic fins. — This was the last fin to form, 

 there being no evidence of it until a bud appeared 

 in a 3.9-mm. specimen. Ossified rays were first 

 formed in a 4.0-mm. specimen, but the full com- 

 plement of 6 (distinguishable as 1 pro-spine and 

 5 pro-soft-rays) was not present until 4.8 mm. 

 Segmentation was first noted by about 6.6 mm., 

 and was complete by about 8.2 mm. Branching 

 had started by 8.2 mm., and was complete at 

 8.7 mm. 



All pelvic fins so examined, 147 pairs, had a 

 count of 1 spine and 5 soft-rays, except for the 

 right fin of a 45.5-mm. specimen (from USNM 

 58831), which had a I, 4 count. Such a variant 

 is extremely unusual in this constant-rayed fin, 

 and the low count was possibly due to an injury 

 to the embryo. 



Scales 



Althougli the smallest prejuvenile (8.2 nun.) 

 was completely covered with scales, the smallest 

 individual on which vertical scale rows were 

 counted was 23.8 mm., and the smallest on which 

 lateral-line scales were counted was 26.4 mm. 

 The full range of adult complement of vertical 

 scale rows and pored lateral line scales was 

 present at appro.ximately these sizes. On tlu> 

 basis of a previous discussion of the phenomenon 



T.\BLE 5. — Variation in counts of pored lateral-line scales 

 and vertical scale rows in 145 specimens of Pseudopria- 

 canthus altus 



[The upper number in each block is the count obtained for that combination, 

 and the number in parentheses below is the approximate percentage of 

 that count in the total sample] 



PORED LATERAL-LINE SCALES 



31 32 33 34 35 36 37 38 39 Total 



35 



36 

 37 

 38 

 39 

 40 

 41 

 42 

 43 

 Total 



(Caldwell, 1957: p. 105), I presume that once 

 the scales are formed in P. altus, the number for 

 that individual remains unchanged. The varia- 

 tion in combinations of numbers of vertical rows 

 and pored lateral -line scales is shown in table 5. 



No scales had formed at 4.8 mm. At 5.3 mm., 

 there were small patches on the lower flank of the 

 belly on each side in the region anterodorsal to the 

 anus, and a small patch near the anterior end of 

 the isthmus. A 6.6-mm. individual was covered 

 with scales except for areas just ventral and 

 posterior to the base of the pectoral fins, on the 

 lower half of the caudal peduncle, and the lower 

 half of the flank of the body above the anal fin 

 and behind the anus. Tlie scales appeared to 

 form first as widely spaced bristles. These soon 

 developed into the upstanding ctenii of the pre- 

 juvenile, and in final development they were 

 strongly ctenoid scales firmly anchored in the 

 scale pockets. 



The lateral-line scales did not form until about 

 25 mm. There was an open channel between the 

 other scales (seen in an 8.2-mm. individual) to 

 mark its course in the smaller fish. The scales 

 adjacent to this channel appeared to join to cover 

 tlie open area as they enlarged, meanwhile devel- 

 oping the pores. 



