335 



which numerous diatoms live (symbiotically ?) ; the surface is 

 covered by particles of mud, etc. This species, which may be 

 found under stones at low tide, occurs also in the Mediterranean. 

 FAM. 6. Sternasjoidae. The single genus, Sternaspis, has not 

 been recorded on our coasts, but is of so peculiar a structure as to 

 deserve a description. 1 S. scutata Eanzani, occurring in the 



Fig. 181. Ster naspis scutata Ranz. x 2. (From Vejdovsky. ) The left figure shows tlie 

 ventral surface ; the right represents the internal organs as seen when the body-wall 

 is pinned aside, having been slit up along its dorsal surface, a, Arms ; c, gills ; ch, 

 anterior strong chaetae ; ch 1 , bundles of chaetae along the lateral margin of the 

 shield ; ch 2 , the posterior marginal chaetae ; d, oviduct ; g, the external tube 

 carrying genital pore; i, coiled intestine; n, nephridium ("brown tube"); o, 

 ovary, amongst the coils of the alimentary canal ; p, pharynx ; pr, prostomium, 

 with mouth just behind it ; s, shield (on left figure) ; s, stomach (on right) ; sh, 

 outline of shield seen through the ventral body-wall (in right figure) ; x, chaetae 

 embedded in the body-wall, with nerves passing by them. 



Mediterranean, is rather less than an inch in length, and derives 

 its name from the possession of a pair of peculiar " horny " plates 

 or shields on the ventral surface posteriorly. Around their 

 margins are set about thirty bundles of long capillary chaetae. 

 There are three half rings of stronger chaetae on each side near 

 the anterior end of the body. The mouth is overhung by a very 



1 Vejdovsky, Denk. Akad. Wicn, xliii. 1882, part 2, p. 33 ; and Rietsch, Ann. 

 Sd. Xat. (Zool.) ser. 6, xiii. 1882, art. 5. 



