94 CONTEIBUTIONS TO NORTH AMERICAN ICHTHYOLOGY — II. 



Leptops, Rafinesque (1820), Ichthyologia Ohiensis, 64. 



Opladelus, Rafinesque (1820), Ichthyologia Ohiensis, 64. 



lUctis, Rafinesque (1820), Ichthyologia Ohiensis, 66. 



Pylodictis, Rafinesque (1820), Ichthyologia Ohiensis, 67. 



Hopladelus, Gill (1862), Proc. Bost. Soc. Nat. Hist. 45, and of most late authors. 



Pelodlchthys, Gill & Jokdan, MSS. — Jordan (1876), Ann. Lye. Nat. Hist. N. Y. — . 



Pimelodus sp., Kirtland, Cuv. & Val. et Auct. 



Etymology. — nrjXog, mud ; ixBvg, fish. 



Type. — Pilodictis limosus Raf. ;= Silurus olivaris Raf. 



Body much elongated, very slender, much depressed, anteriorly 

 broader than high. Head large, very wide and depressed, latterly 

 expanded, above broadly ovate, and in profile cuneiform. Skin very 

 thick, entirely concealing the skull. Supraoccipital bone entirely free 

 from the head of the second interspinal. Eyes small. Mouth very 

 large, anterior and transverse. The lower jaw always projects beyond 

 the upper. Teeth in broad villiform bauds on the intermaxillaries 

 and dentaries. The intermaxillary band is convex anteriorly, and pro- 

 ceeds to the insertion of the maxillaries, where it is abruptly angularly 

 deflected, and proceeds backward as an elongated triangular extension. 

 The band at the symphysis is slightly divided and anteriorly separated 

 by a small triangular extension of the labial membrane. The lower 

 dental is anteriorly semicircular and attenuated to the corners of the 

 mouth. There are about twelve branch iostegal rays on each side. 



The dorsal fin is situated over the posterior half of the interval be- 

 tween the pectorals and ventrals, and has a spine and about seven 

 branched rays. The spine is rather small, and more or less enveloped in 

 the thick skin. 



The adipose fin is large, and has an elongated base resting over the 

 posterior half of the anal ; it is very obese and inclines rapidly back- 

 ward ; it is rather less free posteriorly than in Amiurus. 



The anal fin is small ; it commences far behind the anus, is a little 

 longer than high, and is composed of about thirteen rays. 



The caudal fin is oblong, subtruncated, placed on a vertical basis, 

 and with numerous accessory simple rays, recurrent above and beneath 

 the caudal peduncle. 



The pectorals have a broad, compressed spine, serrated or dentated 

 on its external and internal margins, and with the prolonged fleshy 

 integument obliquely striated. 



The ventrals are rounded and have nine rays, one simple and eight 

 branched. 



