. Bulletin of the United States Fish Commission. Fisheries -- United States; Fish-culture -- United States. 58 BULLETIN OP THE BUREAU OF FISHERIES. The posterior slips of the erector anaUs are somewhat modified from the regular arrangement. The last pair of erector and depressor muscle slips is greatly enlarged, or rather the erector is greatly enlarged and the depressor moderately so. The fibers near the tendon of insertion pass over the modified interhemal cartilage to which the retractor ischii is attached, to insertions into the posterior border of the last anal fin ray. This fin ray is it
. Bulletin of the United States Fish Commission. Fisheries -- United States; Fish-culture -- United States. 58 BULLETIN OP THE BUREAU OF FISHERIES. The posterior slips of the erector anaUs are somewhat modified from the regular arrangement. The last pair of erector and depressor muscle slips is greatly enlarged, or rather the erector is greatly enlarged and the depressor moderately so. The fibers near the tendon of insertion pass over the modified interhemal cartilage to which the retractor ischii is attached, to insertions into the posterior border of the last anal fin ray. This fin ray is itself very small. The tendinous end of the muscle slides over a groove formed by the modified cartilages supporting the ray. At the anterior margin of the series of erector divisions there is a muscular slip which seems to belong to the series, judging by its origin, but the insertion of which passes into the skin in front of the fin and near the base of the anal papilla. The contractions of the erector muscles tend to elevate the anal fin and in con- tinued contraction to hold it in the erect position. This is favorable in increasing the. Fig. 13.—Superficial muscles of the aual fin. inc., inclinator analis showing divisions lor each ray; re. i., retractor ischii (pro- tractor aaahs): r. a., retractor anahs; Lai., great lateral muscles. The dotted line indicates the ventral limit of the lateralis superficiahs. efficiency of the lateral movements which this fin contributes in balancing the fish in the water. The contractions of the larger posterior muscle slip described tend to draw the pos- terior end of the anal fin sharply against the body and to some extent to antagonize the retractor analis. The function of the most anterior slip which has an insertion into the skin in front of the fin would seem to be in connection with the movements of the anal papilla. DEPRESSOR ANALIS. The depressor muscle consists of a series of slips which arise from the anterior surface and lateral
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