PODOPLEA ISOKERANDRIA 



71 



Echinoderms, Annelids, Molluscs, and Tunicates. Lichomolgus 

 agilis (Fig. 38) occurs in the North Sea, Atlantic, and Mediter- 

 ranean, on the gills of large species of 

 the Nudibranch, Doris, while L. aliens 



is found in the peribranchial cavity and / V«?'* 



cloaca of various Ascidians. Sabel- 

 liphilus may infect the gills of Annelids 

 such as Sabella, and is common at 

 Liverpool. 



Fam. 4. Ergasilidae. — Tkersites 

 (Fig. 39) is parasitic on the gills of 

 various fishes, e.ff. T. gasterostei, which 

 is common on Gasterosteus aculeakis 

 on the French and North Sea coasts, 

 and may even be found on specimens 

 of the fish that have run up the Eiver 

 Forth into fresh water. The animal Fio- 38. — Lichomolgus agilis, 

 possesses claw-like second antennae by ^egn^^ntf cji/t Jep.rtw! 



which it clings to its host. ^''■■-'> l^t thoracic segment ; 



o • -1 1 1 , ■ T 1 1 Th.5, 5th tlioracic j 



bimilarly characterised by the (After Cami.) 



-Anl.S. 



FiQ. 39. — Thersif.es gasterostei. A, 

 9, X 10; B, <J, X 20. Abd. 

 1 <Sj 2, Fused 1st and 2nd ab- 

 dominal segments; Ant.l, Ant. 2, 

 1st and 2nd antennae ; e.s, egg- 

 sac ; Th. thoracic appendages. 

 (After Gerstaecker. ) 



--Abd.tiS. 



absence of a siphon are three other families of fish-parasites, the 

 Bomolochidae, Chondracanthidae, and Philichthyidae. 



Fam. 5. Bomolochidae. — Bomolochus (Fig. 40), parasitic on 

 the skin of the Sole (Solea) and in the nostrils of Cod (Gadus), 

 is held to be related to the Ergasilidae. The first thoracic limb 

 is remarkably modified. "Were it not for the absence of a siphon, 

 it would be hard to separate this family from the Caligidae. 



