476 F. W. GAMBLE. 



and tlie third across the tail. v. Graff, in his Monograph, 

 pi. xviii, fig. 6, has figured eight different varieties of the 

 arrangement of these bands, which he observed in a single 

 gathering among Ulva at Millport ; and this does not exhaust 

 the possible cases. Small specimens (-5 — 1 mm.) with a yellow 

 ground-colour (due apparently to the contents of the gut-cells) 

 are not uncommon. Since the ''key " for the determination 

 of species of this genus in v. Graff's Monograph is largely 

 dependent on the arrangement of the pigment, these varieties 

 are at first very troublesome. Moreover Vorticeros auricu- 

 latum (which frequently occurs among Plagiostoma vit- 

 tatum) with retracted tentacles, can be in no way anatomically 

 distinguished from a common variety of Plag. vittatum, in 

 which the pigment is present over the greater part of the 

 dorsal surface. With regard to the internal anatomy I can 

 confirm the accounts of v. Graff and Jensen (49). Van 

 Beneden (33), the first to discover the stalked yellow- 

 brown egg-capsules, found them attached to the abdominal 

 feet of the lobster. At Plymouth they were abundant in 

 September on the sides of a vessel containing several indi- 

 viduals. 



Habitat. — Apparently more abundant on our northern than 

 southern coasts. Millport, abundant (v. Graff) ; Plymouth ; 

 Port Erin, Isle of Man (F. W. G.). 



Distribution. — Faroe Islands (Schmidt), Bergen (Jensen), 

 Heligoland (Leuckart, 23), Walcheren, on coast of Belgium 

 (Slabber),^ Ostende (van Beneden), Wimmereux (Hallez). 



38. Plagiostoma koreni, Jensen. 



Length 1'4 mm. Body similar in shape to Plag. vit- 

 tatum, but smaller, and rather narrower in front. The first 

 half of the body is white, and behind this a broad transverse 

 brown band (due to reticular pigment) over the dorsal surface 

 and the sides. Behind this again are scattered brown spots. 

 The brain, which bears two red eyes, is placed in front of 

 ' ' Physikalisclie Belustigungen,' Niirnberg, 1775, pp. 31 and 36, 



