458 F. W. GAMBLE. 



Subfamily EuMEsosTOMiNiE. 



Mesostomidse with one common genital pore, a 

 single germariura, two vitellaria and accessory 

 organs. Testes long. Excretory vessels opening 

 into the pharyngeal sheath. 



Genus 10. — Mesostoma, Duges. 



Without otolith. Copulatory organ traversed 

 throughout its entire length by the ducts of male 

 secretions. 



19. ? Mesostoma neapolitanum, v. GrafiP. 



Length '5 mm. Body flattened behind, bluntly pointed 

 in front, white. Between the eyes are two tracks formed by 

 masses of large curved rhabdites. Smaller ones are present 

 elsewhere. Pharynx small, in front of the centre. Intestine 

 large, filling up the greater part of the body. Eyes two, with 

 lenses. Genital pore close to the hinder end. Testes 

 lateral. The penis bears a funnel-shaped terminal portion 

 which receives the contents of the vesicula granulorum, and 

 in front of this lies the serai-lunar vesicu la seminalis. The 

 atrium did not appear to be so large as in v. Graff^s specimen. 



Habitat. — Among Fucus, Plymouth Breakwater (E. W. G.). 



Distribution. — Naples (v. Graff). 



I append a query to this species, since my observations were 

 made on one specimen, and agreed more closely (but not en- 

 tirely) with M. neapolitanum than with any other species. 

 More specimens of this marine Mesostoma are greatly needed, 

 as its position is not thoroughly defined. 



Family PROBOSCID^. 



Rhabdocoela with tactile proboscis; one or two 

 genital pores. Gerraaria and vitellaria distinct. 



