THE ANATOMV OF PLEUROTOMARTA BEYRICHIT. 215 



The Anatomy of Pleurotomaria Beyrichii, 



Hilg. 



By 



Martin F. Woodward, 



Demonstrator of Zoology, Royal College of Science, London. 



Witli Plates 13—16. 



The vast antiquity which characterises the genus Pleuro- 

 tomaria — for no one can doubt the identity of the living and 

 fossil shells which are customarily grouped together under 

 this name — has justly endowed this mollusc with great 

 interest for those studying the ancestry of the Prosobran- 

 chia. When, therefore, a living example was obtained by 

 Agassiz in 1871, and later in 1879 several specimens of both 

 P. Quoyana and P. Adansoniana were dredged by the 

 United States steamer " Blake," the result of an investiga- 

 tion of the anatomy of these forms was awaited with great 

 interest. Unfortunately, however, the specimens all turned 

 out to be in a bad state of preservation, and although falling 

 into such skilled hands as those of Dr. Dali, it was found 

 impossible to make out much of their anatom}'. Dall, how- 

 ever, published ^ figures and descriptions of the external cha- 

 racters of the animals, of the radulas and of some few points in 

 connection with the pallial complex, the rest of the body 

 being too much decomposed for investigation. 



During the last few years a further examination of one of 



> " Report on the Mollusca dredged by the United States steamer ' Blake,' " 

 'Bull. Mus. Conip. Zool., Harvard,' vol. xviii, 1889. 



