TETHYS DACTYLOMELA (RANG) 17 



tinued downward to the mouth, the tips auriculate, their posterior 

 margins forming a prominent flap closely applied to the anterior 

 portion. 



Just below and in front of the bases of the rhinophores the 

 minute black eyes shimmer through the integument. 



Reproductive opening. The male genital opening lies just 

 below the base of the right anterior tentacle, a strongly defined 

 groove extending backward from it and dorsally between the para- 

 podia to the hermaphroditic orifice in front of the base of the 

 branchia. This groove is marked by a narrow black line on its 

 right margin throughout its whole length. Behind and below 

 the genital opening is a large conspicuous circular orifice, the 

 opening of the hypobranchial gland, or gland of Bohadsch. 



The anal opening is situated upon the base of the posterior 

 wall of the siphon, presenting a pocket-like appearance. 



The renal opening is small and slit like, 1.2 mm. in length, 

 and lies deep in the mantle cavity above the posterior end of the 

 ctenidium, some distance in front of the anus. 



Foot. The foot is broad and well developed, its anterior end 

 rounded, the posterior one more bluntly pointed. Its margin is 

 clearly defined in all the specimens, its well developed muscula- 

 ture being contracted, giving it a firm rugose texture, in contrast 

 to the smooth soft surface of the remainder of the body. 



In the literature scarcely anything is to be found upon the 

 internal anatomy of this species, a fact too frequently true of the 

 majority of the members of this family, many of them having 

 been described by the shell alone, which, as Pilsbry has pointed 

 out, is probably the least characteristic organ of the animal. The 

 interrelations of this widely distributed group cannot at present 

 even be approximated on account of this lack. With a view to 

 aiding in filling up this gap in our knowledge I have made detailed 

 dissections of the Aplysiidae found in this collection. 



INTERNAL ANATOMY. 



In the description of the internal anatomy, unless otherwise 

 stated, all of the measurements given are taken from an individ- 

 ual of 70 mm. total length in the well preserved alcoholic specimen. 



The body wall is similar to that of other members of the 

 group, the external integument being reinforced by interlacing 



