8 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



another that their separation is doubtful. There 

 is a Pacific species so similar to nicaragitensis and 

 leucas that conunercial shark fisliermen who fished 

 on both coasts claimed they were unable to dis- 

 tinguish one from the other except by area of 

 capture. I do not know the scientific name for 

 the form if it has a name, but whatever the 

 species, it is like nicamgucnsis or leucas and not 

 like mUherti. Meek and Hildebrand seemingly 

 had difficulties with this one in Fishes of Panama 

 (1923), wherein they discuss a Pacific species 

 Carcharh'mus azureus (Gilbert and St arks) as a 

 synonym of rrdlberti. But Meek and Hildebrand 

 did not see a specimen from the area which they 

 themselves could identify as inUberti and the 

 significant sentence in their treatment states — 



We certainly must regard the present arrangement as 

 tentative only, for more specimens must be compared 

 before the true affinities of the specimens from the op- 

 posite coasts can be established. 



A paper by Rosenblatt and Baldwin (1958) on 

 some of the carcharhinids of the eastern Pacific 

 presents for the first time information on the 

 presence or absence of the middorsal ridge in 

 Pacific species. This is an important contribution 

 and includes more comprehensive descriptions 

 than have hitherto been available for sharks of 

 the eastern tropical Pacific. These authors find 

 the separation of Eulaonia from Carcharhinus 

 unacceptable for Pacific species. In support of 

 this an vuifortunate choice of illustrative argu- 

 ment is used. They say C. altima, for example, 

 has a definite dermal ridge but teeth which are as 

 narrow as those of any member of the smooth- 

 backed group (Springer, 1950). This is an error. 

 The teeth of altma in the upper jaw are similar 

 in general shape to the teeth of the other species 

 of Eulamia. These authors logically call atten- 

 tion to the ill-assorted group left in the genus 

 Carcharhinus by my 1950 revision, mentioning 

 leucds and velox as examples. I am in complete 

 agreement with this but find no cogent argument 

 for the elimination of Eulamia^ since the species 

 of Eulamia as resti'icted are remarkably similar 

 to one another in all of their morphological fea- 

 tures. The sharks allied to the genus Carchar- 

 hinus are far too widespread and numerous and 

 there is far too little known about them for an 

 adequate study of the entire group. Additional 

 revisions of the group are needed. 



Differences between adults of E. altima and 

 inilhertl are quite apparent in field examination 

 wlien the two are seen side by side. The snout of 

 altima is longer and notably thicker dorsoven- 

 trally. Furthermore, the first dorsal fin in E. 

 altima looks quite different because it is not quite 

 so far forward as in E. milberti and is neither so 

 erect nor so high. The high and erect dorsal fin 

 of E. milierti in a forward position (fig. 2) is a 

 reliable and adequate character for field recogni- 

 tion of adults in the water, if the size of the 

 shark is taken into consideration. 



Gill (1862) based his classification of the car- 

 charhinid sharks almost entirely on the structure 

 of the teeth. His arrangement of genera was not 

 satisfactory and it is apparent that short descrip- 

 tions of shark teeth are inadequate and lead to 

 confusion even though the number and form of 

 the teeth show comparatively little variation 

 within species and are of considerable diagnostic 

 value. The persistence of essentially similar 

 shape and structure in the successively larger 

 teeth appearing in some carcharhinid sharks as 

 they grow has been fairly well established by ob- 

 servation. In E. milierti, at least, this appears 

 to be true, although this is neither universal 

 among sharks nor adequately demonstrated for 

 many species. 



To obtain some verification of the extent of 

 variation in the number of tooth rows in car- 

 charhinid sharks, I took advantage of a situation 

 requiring the preparation of several hundred 

 clean, dry shark jaws for a commercial order. I 

 carefully identified the sharks and tagged the 

 ^^jaws of a series of 110 E. milierti together with 

 all other sharks appearing at the same time on 

 the dock at Salerno, Fla. All of the milberti and 

 most of the other sharks were adults ; sex was not 

 noted. After the jaws were cleaned I counted 

 and recorded the number of tooth rows (table 1). 

 To the extent thut this sample represents the 

 population of milberti, the counts of rows of 

 teeth indicate that variation is small in that 

 species. 



The shape and the relative position of the fins 

 in carcharhinid sharks are reasonably useful 

 characteristics for identification. Small differ- 

 ences in the size of fins or even in their positions, 

 however, are of comparatively little value because 

 of differential growth and the diverse trends this 



^^^r 



