Kntozon of Britinli Murine Fishea. 61 



other species of the genus did not admit its inclusion with 

 any of thoin. It thus t'.ilJM to he de-^rrihed as a new spfcios. 



The following^ (l(>scription as well as the fi;;ure are rrom 

 the preserved specimen, so that the measurements may 

 admit of modification : — 



The hody is depressed, elon{;ate-ovate, somewhat attenuate 

 in front, rounded hehind, with a small hut distinct terminal 

 prominence. Length .'i3 1 mm. : maximum hreadth (at 

 ventral sucker) '7") mm, Ant-acetahular repjion (neck) com- 

 prises \ of lenj^th of l)ody. Anteriorly the cuticle is heset 

 with numerous irrcfrularly arranged sjjines, becomiuf^ fewer 

 hehind the ventral sucker and absent from the greater part 

 of the post-aeetahular re*j:ion. Closely apposed to the margin 

 of the oral sucker are two rows of large spines. The spines 

 in the first row are shorter than those in the second, the 

 lengths being about 'O-Sl mm. and "037 mm. respectively, 

 but there is some variation. The number and disposition of 

 these spines are characteristic of the species, and serve to 

 distinguish it from other species of the genus. They occur 

 in two regular uninterrupted rows ; there are 28 spines in 

 each row, making a total of 56, and the spines of one row 

 alternate with those of the other. In no other species are 

 the spines so numerous, the nearest approximation being 

 48, as recorded by Looss in Stephanochasmus caducus, Lss. 

 Steph. pristis, Dcslongch., according to Looss, has 30 spines. 

 A point which Looss lays stress on is that in his examples 

 of Steph. cesticillus the second row of spines numbers one 

 less than the first. This is due to the absence of a spine of 

 the second row in the mid-ventral line. No such arrange- 

 ment occurs in Steph. haccatus; each row is complete, so 

 that there is no gap in the mid-ventral line. In Steph. ces- 

 ticillus, moreover, the spines of the first row are longer 

 than those of the second. Between the two species another 

 feature of difJerence presents itself in the disposition of the 

 other euticular spines. In Looss's figure these do not start 

 immediately behind the cephalic spines, so that a small 

 triangular bare area is left. This (iocs not occur in Steph. 

 baccatu.'i, for irregular scattered spines are seen on the neck 

 immediately behind the cephalic spines. 



The suckers are comparatively small and not very mus- 

 cular. The oral sucker is terminal and cup-shaped; its 

 diameter is "SS mm., while the aperture is "19 mm. At the 

 lateral margins of the rim, projecting into the aperture, a 

 little nodule is apparent. \Vliether this is a natural con- 

 dition or the result of preservation 1 am unable to say. The 

 ventral sucker is at a distance of '87 mm. from the antt-rior 



Ann. tfr Mag. S\ Hist. ►Scr. 7. Vol.x'ix. 6 



