48 Synopsis of the Fresh Wate?' Fishes, 



long and slender spines, with hooked apices ; this tuft is nearly 

 concealed in a fossette under the operculum when it is de- 

 pressed. 



Month moderate, with the labial veil semi-ovate and entire, 

 narrow and nearly straight in front, broad and with a rounded 

 margin behind ; the inferior surface of the veil is covered by 

 conical papillie. 



Teeth slender with hooked apices. 



First dorsal sub-quadrate, little longer than high, and gene- 

 rally supported by eight rays ; its anterior portion, or the mid- 

 dle, is placed opposite the bases of the ventrals. 



A^ial small, consisting of from three to six rays. 



Pectorals large, with the first rays robust, and covered with 

 prickly spines. 



Yentrals moderate, with the first rays claviform, as in the 

 pectorals, but much more slender. 



As we have above restricted the genus Ancistrus, the Hypo- 

 stomus duodecimalis of Yalenciennes, and H. multiradiatus of 

 Hancock will be excluded. For those and the allied species 

 described by Dr. Kner, we would propose a new genus under 

 the name of Pterygoplichthys, intending by that name to allude 

 to the many-rayed dorsal of those fishes, which are singular 

 among the Goniodonts by the presence of twelve or more rays 

 to that fin. They are also distinguished from the true Ancistri 

 by the presence of small plates on the abdomen. The genus 

 Ancistrus seems to have been framed with especial regard to 

 those fishes to which the name is here restricted, and is by Dr. 

 Kner divided into two sections, which correspond to Ancistrus 

 and Pterygoplichthys, his section « answering to the former 

 genus, and jS to the latter. 



