Boone, Mollusca, Cruises of "Ara" and "Alva" 359 



first pair of arms, are distinctly the strongest and stoutest pair, 

 being about 6.75 times as great as the combined length of the head 

 and body and very attenuate ; the second and third pairs of arms 

 decrease gradually in length, the fourth, or ventral pair, being 

 only 0.65 as long as the first pair. The suckers are discoidal, of 

 moderate size, set in alternate dual series, somewhat crowded, the 

 cupules deep ; the largest suckers occur on the arm, a short dis- 

 tance beyond the web margin, and are of a diameter equal to about 

 one-half of the arm diameter at this point. On the attenuated 

 distal portion of the arms, these suckers are numerous, quite small, 

 but strong. The hectocotylized arm is only 0.65 as long as its com- 

 panion. The terminal organ is about 0.4 of the arm length. The 

 ligula is an elongate-conic, conspicuously thickened and expanded, 

 spoon-shaped article, with the inner surface moderately, widely 

 excavate and marked with about ten irregular, transverse laminae 

 copulatoriae. 



The web is brief, attaining the maximum depth between the 

 arms of the first pair, the sections between the first and second 

 pairs of arms being nearly equal thereto, the third and fourth sec- 

 tions of the web gradually decreasing in depth, while the fifth sec- 

 tion of the web, between the arais of the fourth pair, is quite 

 shallow. 



The texture of the skin is generally smooth on the ventral sur- 

 faces, but is very coarsely and irregularly papillose on the dorsal 

 surfaces, these papillae frequently assuming the arrangement of 

 longitudinal lines, frequently forming conspicuous ridges, espe- 

 cially on the body and web, adding to the grotesquerie of the octo- 

 pus' appearance, especially when the creature is in a pugnacious 

 state. 



References : Octopus ornatm, Gould, A. A., in Wilkes, C, United 

 States Explor. Exped., Mollusca, 1852, vol. XII, p. 476, pi. 48, 

 figs. 590 and 590a, atlas, vol. XII. — Tryon, G. W., Man. 

 Conch. 1879, vol. I, p. 112, pi. 30, figs. 29, 30.— RoBSON, G. C. 

 R., Monogr. Recent Cephalop. Coll. Brit. Mus. Nat. Hist., pt. 

 I, Octopodidae, 1929, p. 198. 



Polypus ornatus, Berry, S. S., Proc. U. S. Nat. Mus., 1909, vol. 

 VII, p. 418; Bull. U. S. Bur. Fish., vol. XXXII, 1914, p. 294, 

 pi. 46, text fig. 14. 



