278 s. GOTO. 



penis spines, wlncli were all of the same size and form, 

 measuring 0.66 mm. in length. Each spine consisted of two 

 portions, a distal awl-shaped part with an expanded base, and 

 a handle-like part consisting of two slender filaments (fig. 18). 

 In Folyst, ohlongum Wright there are 16 penis spines, but these 

 are alternately small and large. Hence, Leidy's P. ohlongum 

 is not identical with P. ohlongum Wright ; nor can it be referred 

 to the species here described, the form of the penis spines being 

 very different. It must be a new species ; but it would be use- 

 less to name it in the absence of any adequate description. 

 The new species here described was found by Dr. A. Hassall of 

 Washington in the urinary bladder of Kinosternon pennsylvanicum 

 in Bowie Prince George County, Md. My best thanks are due 

 to Dr. Hassall for kindly giving me several of the specimens. 



Microcotyle pomatomi n. sp.* 

 (PI. XXI, fig. 27). 



Body symmetrical, elongated ; length 4 mm., of which 

 nearly the posterior one-third bears about 70 suckers on either 

 side and dofts _^not contain any internal organs, except the ter- 

 minal portion of the intestine ; the sucker-bearing portion pro- 

 jecting a little in front on the ventral side. Oesophagus of 

 moderate length, terminating a little behind the common genital 



* I may take this opportunity of replying to Drs. Parona and Perugia, who criticise me 

 for " neglecting," in my descriptions of tlie new species of Mia^ocotyle, the chitinous armature 

 of the genital atrium, which to tliem constitutes " il carattere veramente differenziale delle 

 varie specie" ['96, p. 3]. If, now, one turns to my "Studies," to which the above criticism 

 refers, one will see that I devoted no^less than four full pages to the description of the genital 

 atrium, including the spines, of Microcotyle in the anatomical part, and then again gave the 

 points peculiar to each species in tlie systematic portion. I must at the same time express 

 a warning against taking any single character, however decisive it may appear to be at the 

 time, as the criterion for determining species. The agreement of a single character does not 

 always prove identity of species. 



