41 8 Memoir Sears Foundation for Marine Research 



gin moderately concave, the free rear tip not very slender, about V3 as long as the base; the 

 midpoint of base only about Yo as far from axil of pectoral as from origin of pelvics and 

 the rear tip anterior to latter by a distance about Vs as long as the base (this distance is con- 

 siderably greater relatively in zygaena). Second dorsal about Vs as long as ist at base but 

 only about V5 as high, its origin about over midpoint of base of anal, with narrowly rounded 

 apex and only weakly concave posterior outline, its noticeably slender free rear corner 

 nearly twice as long as base and about twice as long as the vertical height. Distance from 

 tip of 2nd dorsal to precaudal pit a little less than Vs as long as base of 2nd dorsal (nearly 

 or quite as long as base of 2nd dorsal in zygaena). Caudal a little less than V3 (about 3 1 to 

 33%) of total length, its upper margin only very slightly convex, the terminal sector about 

 Vs the length of fin, narrow-triangular, with subacute tip and rather deeply concave lower 

 posterior margin; the lower lobe a little more than Ys as long as upper with weakly convex 

 anterior and posterior margins and subacute tip; the re-entrant contour (included by the 

 two lobes) with rather abruptly rounded corner and a little more than a right angle. Dis- 

 tance from origin of caudal to tip of anal a little less than V2 as long as base of anal. Anal 

 about 1 .4 to 1 .7 times as long at base as 2nd dorsal, about i .0 to i .4 times as high vertically, 

 its anterior margin much more convex, posterior margin more deeply concave, apex acute, 

 free rear corner less slender than that of 2nd dorsal, about % as long as the base, its tip 

 considerably anterior to that of 2nd dorsal. Distance from origin of anal to tips of pelvics 

 only about V2 as long as base of anal. Pelvics with nearly straight margins and narrowly 

 rounded corners, and about as long at base as anal. Pectoral a little less than % (about 57 

 to 61%) as long as head, a little more than V2 (about 56%) as broad as long, the outer 

 margin moderately convex toward tip, distal margin weakly and uniformly concave, the 

 apex and inner corner very narrowly rounded. 



Color. Light gray above shading to white below, the pectorals tipped on their ventral 

 surfaces with black in life. 



Size. The Study Material (p. 415) suggests that diplana may be born at a length 

 no greater than 400 to 450 mm. Males mature at about 1,800 mm. (about 6 feet), and 

 grow to at least lO feet; it is not known how much larger. 



Developmental Stages. Embryos have not been described as yet, except for the teeth 

 (see p. 417), nor have we seen any. 



Habits. Recognition of the fact that diplana is distinct from zygaena is so recent^" that 

 no attention has yet been devoted to its life history as contrasted with that of zygaena. 

 Neither do the few records of Hammerheads that can be positively referred to it con- 

 tain any pertinent information. It is probable, however, that the account of the habits, food, 

 etc., of zygaena (p. 441) applies equally to diplana, at least in a general way. Gravid 

 females have been taken in southeastern Florida waters." 



Range. Tropical and warm-temperate Atlantic, probably including the Mediter- 



10. It was unmistakably pictured by Valenciennes more than a century ago (Mem. Mus. Hist. nat. Paris, 9, 1822: 

 pi. II, fig. i) as Zygaena malleus. 



11. Personal communication from Stewart Springer. 



