TAYLOR : ON TESTACELLA SCUTULUM. 34 1 



also, but a single retractor muscle to this organ in scutidtim and 

 maugei, while haliotidea has in addition one and sometimes 

 even two slender lateral retractors. The difference in size of 

 the female organs, as represented in the figures, is chiefly due 

 to unequal sexual development in the specimens examined, 

 and is not a matter of importance. 



The enormous ungual sheath tapers off behind into a very 

 powerful muscle, or combination of two, three, or four partially 

 independent ones, and has in addition its hinder half attached 

 laterally to the skin of left side, near the dorsal line, by a series 

 of ten to twenty conspicuous muscular bands, running parallel 

 to each other and fixed at independent points, T. saihduvi 

 differs from haliotidea in this character, insomuch that these 

 lateral muscles, though variable in number, are constantly less 

 numerous than in haliotidea^ where they generally exceed twenty. 

 T. maugei has terminal muscles only. 



The LINGUAL RIBBON of a specimen of T. scutuluin from 

 Chiswick, collected by Mr. S. C. Cockerell and prepared for me 

 by Mr. Neville, contains 46 rows of teeth, with 34 in each row, 

 totalling 1564 teeth, while a specimen of T. haliotidea sent us 

 from Oxford by Mr. E. B. Poulton, has only 38 rows, each con- 

 taining 36 teeth, or a total of 1368. In all our British species 

 of Testacella there seems to be a tendency to develop along 

 the medial line a central rudimentary tooth. The angle 

 formed by the convergence of the rows of teeth towards 

 the centre of the ribbon is much more acute in haliotidea 

 than in scutulicin. 



IS 



s 



s 



Teeth of T. haliotidea x 40. Teeth of T. scutulum x 40. 



The teeth of T. scutuluin differ from those of haliotidea in 

 being more slender, not so much curved, and with the barbed 

 end not nearly so large and strong, while the prominently de- 



