254 KEPORT OF THE COMMISSIONER OF FISH AND FISHERIES. 



Shell consisting- of 2 valves, superior and inferior in position 5 ridge 

 present, forming continuation of tail. The tail in this species is a 

 shell process, consisting of 2 halves, a superior and an inferior, each 

 connected with and forming a solid process of the corresponding valve. 

 Length of tail, 38 /< . Valves separating very slowly in sulphuric acid 

 (cold, concentrated), the gradual lateral shifting of one valve over 

 another beginning within a few minutes and continuing for 20 or 30. 

 Coincidently the two tail halves diverge, serving well as indices of the 

 amount of lateral sliiftiug of the valves. Iodine fails to loosen the 

 connection of the tail (or of either half) with the valves. 



Capsules long, narrow, parallel-appressed ; capsular index about 0-40 ; 

 walls rendered transparent and filaments visible by iodine water. 



Sporoi)lasm showing the usual anterior extension of the supero- 

 median cornu. The other cornua are also recognizable. Vacuole pres- 

 ent, subcircular in outline, usually placed toward the anterior end of 

 the sporoplasm. As regards nuclei, hydrochloric acid alcohol carmine 

 always stains as many as and usually 2, rarely 3; position inconstant, 

 one or both being either before or behind the vacuole. In addition, 

 there are constantly present, at or ciose to the extreme posterior end 

 of the sporoplasm, 2 deeply stained dots, which are too minute to show 

 any structural details. 



Habitat. — 7 or 8 cysts at bases of the spines of the second dorsal fin 

 of Amciurus melas Raf. (bullhead) from Storm Lake, Iowa, collected 

 August 23, 1890,by Prof. Seth E. Meek, to whose kindness I am indebted 

 for the specimen. 



This species can only be compared with the next. The following 

 summarizes Miiller's scanty diagnosis of that iorm : 



Body very narrow, 3 to 4 times as long as broad; capsules parallel- 

 appressed; tail simi^le, occasionally double. 



The present species answers to all of these characters, but they are 

 too few to warrant the fusion of the two forms, although their identity 

 may be strongly suspected. If established, their identity would con- 

 stitute a very interesting fact, both in zoological and in geographical 

 distribution, for we should then have a species found (so far) confined 

 in its zoological range within the Siluridce and with a very wide geo- 

 graphical distribution.^ 



1 For the geographical distribution (inSouthAmerica)of/?. seta; and of P. fascia fiim, 

 see Eigenmann & Eigenmann, Revision So. Amer. Nematognatbi (Occas. Pajjers Calif. 

 Acad. Sci., San Franc, 1890), pp. 123, 209. Considering the names used by Miiller, 

 the date of his writing, etc., it seems ratlier probable that his localities were those 

 known to Cuvier and Valenciennes (1840), viz, for li. aebce, Surinam, Cayenne, Rio 

 Janeiro, Buenos Ayres, and for P. fasciatiim, Surinam. 



