IN THE PARAGUAYAN LEPIDOSIEEN, ETC. 361 



discrepancy in the statements of different writers. According to Owen [25], Peters 

 [34], McDonnell [21], and Wiedersheim [41], there are six branchial arches. Newton 

 Parker [33] states, however, that there are but five, and is apparently doubtful as to 

 the existence of the arch which Wiedersheim (I. c, p. 56, fig. 8) figures and describes 

 as situated in front of the first cleft and forming the first of the series of six. There 

 is also some obscurity as to the existence of a hyobranchial or hyoidean cleft. Neither 

 Owen nor Peters is explicit on this point, although from their statements as to the 

 position and relations of the gill-filaments and branchial clefts the absence of a hyoidean 

 cleft may perhaps be inferred. Wiedersheim figures (I. c. fig. 8) the first cleft as 

 situated between his first and second branchial arches, but there is no special reference 

 in the text to the presence or absence of a hyobranchial cleft. On the other hand, 

 according to Newton Parker {I. c. pp. 161-162), a hyobranchial cleft is present, 

 and has in relation with its anterior wall the hyoidean hemibranch or " opercular 

 gill." 



On examining the branchial region of a specimen of Protopterus 31 cm. in length, I 

 had no difficulty in detecting the presence of an extremely slender, unsegmented, 

 cartilaginous filament, 7 mm. in length and rather less than 1 mm. wide, situated 

 immediately in front of the first branchial cleft and forming its anterior boundary. 

 The mucous membrane covering the posterior margin of the filament carried a series of 

 minute tooth-like projections, similar to the single row of the second arch and to the 

 double series found on the anterior and posterior margins of the succeeding arches, with 

 the exception of the last, which has but a single row. The cartilage occupies a position 

 precisely similar to the first branchial arch in Lejridosiren, being in close relation with 

 the hinder margin of the suspensorial cartilage, dorsad and posterior to the proximal 

 extremity of the hyoicl arch. It is scarcely open to doubt that this slender cartilaginous 

 rod represents the first of a series of six branchial arches, and, as there is certainly no 

 cleft anterior to it, the conclusion that the hyobranchial cleft has undergone total 

 suppression necessarily follows. It may be mentioned that Pinkus (I. c. p. 318) records 

 the presence of a small piece of cartilage embedded in the oral mucous membrane 

 opposite the first gill-arch. The cartilage is apparently very small, being only 108 mm. 

 in length in a specimen 14 cm. long, and 2 - 36 mm. in one 17 cm. in length. " Sein Bau 

 entspricht genau dem der ubrigen Kiemenbogen, nur dass es bloss eine, und zwar 

 mediale, Reihe zahnartiger Zacken tragt, deren die ubrigen Bogen je zwei, eine mediale 

 und eine laterale, besitzen." After discussing the relations of the cartilage to the 

 branches of the Glossopharyngeal and Vagus nerves, Pinkus concludes : — " Ich recline 

 diesen rudimentaren Kiemenbogen bei der Zahlung nicht mit, sondern zahle, der 

 Innervation und dem ublichen Schema entsprechend, den darauf folgenden Bogen als 

 ersten Kiemenbogen. Demnach liegt die erste Kiemenspalte zwischen diesem Kiemen- 

 bogen und dem Hyoid, die zweite Kiemensplate zwischen diesem Kiemenbogen und 

 dem zweiten Kiemenbogen " (p. 318). I am not quite certain that the cartilage Pinkus 



