91 



and the female differs in nothing from the male. The teeth are 

 precisely similar to those of the " Tintureira" (C. glaucus, Cuv.) 



The " Marraxo" proves to be, as I suspected, Larnna cornubica, 

 Cuv., adult, or of large size. 



Gen. ACANTHIDIUM. 



Corpus gracile, elongatum. Spiracula magna. Pinna dorsales 

 duse, antice spiniferse ; secunda majore postica, caudse approximata. 

 Pinna analis nulla. Pinnts ventrales, subposticae s. secunda dorsalis 

 subanteriores. 



Denies utriusque maxillse dispares, parvi : superioris laniarii, plano- 

 triangulares, tenues, acuminati ; acumine recto ; basi utrinque den- 

 ticulo aucto ; antice triseriati, lateribus biseriati : inferioris incisorii, 

 acumine utrinque a medio oblique deflexo, uni- vel bi-seriati. Cauda 

 oblique oblonga, apice truncata. 



This new genus appears exactly intermediate between the esta- 

 blished genera of Cuvier, Spinax and Centrina : agreeing with the 

 former in its elongated form, and with the latter in the teeth. 



The ventral fins are placed more backward than in Spinax, but rather 

 forwarder than in Centrina, i. e. neither halfway between the two 

 dorsal fins, nor opposite the second dorsal fin, but just before the 

 second dorsal fin, which begins exactly opposite the termination of 

 their base. The tail or caudal fin resembles that of Spinax, rather 

 than of Centrina, and the spines of both the dorsal fins are reflexed 

 as in Spinax, forming the fore-edge of each fin. The pectoral fins 

 are abruptly truncate. The second dorsal fin is greatly larger than 

 the first ; in which it differs equally from Spinax and Centrina. 

 The teeth are not arranged quincuncially, but behind each other in 

 rows. 



Two species have occurred, both of which have hitherto been con- 

 founded with Centrina. 



AcANTHiDiuM pusiLLUM. " Gata negra." A. totum atrum, 

 pusiUum : rostro crassiusculo : denlihus inferioribus uniseriatis : 

 spiraculis oculo remoiiusculis. 



Centrina? nigra, nob. olim in Proceed. Zool. Soc. 18.33, p. 144*. 

 Syn. Mad. Fish in Trans. Zool. Soc. p. 194. Rariss. 



Four individuals of this curious little shark have now occurred, 

 agreeing equally in the foregoing characters and in their dimensions, 

 varying in length only from eleven to twelve inches. The second 

 dorsal fin is somewhat forwarder or more distant from the origin of 

 the tail than in the next species. 



The condition of the teeth, and constancy of size, both indicate 

 an adult fish ; and a comparison of the present species with the 



* A serious erratum has been caused here by the transposition of a sen- 

 tence. The paragraph referred to should stand thus: " It (Centrina} 

 nigra) is intermediate in characters between Centrina, Cuv., and Acanthias, 

 Risso, having the teeth of the former genus as well as the backward posi- 

 tion of the second dorsal (rectius ventral) fin, and the_form of body of the 

 latter." 



