56 



genera only pereopods VI and VII or conversely pereopods III-VII, ter- 

 minate in a spoon-shaped depression accommodating a wholly or partly 

 retractile claw. Rarely, these formations are very weakly developed and 

 almost inconspicuous. The uropods have free rami. The telson constitutes 

 1/3-1/2 the length of the basal segment of uropods III or is somewhat 

 longer. 



A typical deepwater family. Its species usually do not ascend 

 higher than 200-500 m. Only two close species, Lanceola felina and 

 L. intermedia, live in surface waters; rarely one comes across the highly 

 eurybathic L. sayana. 



Lanceolids are parasites and partly commensals of deepwater 

 coelenterates — medusae and siphonophores. Their guts are usually 

 filled with a brownish-red mass — the host tissue containing numerous 

 cnidoblasts. In large crustaceans the guts contained fragments of 

 chaetognaths and even pieces of cephalopods with tentacles and 

 luminous organs. Apparently, the fragments of these animals could 

 have been pulled out by the crustaceans from the trapping filaments 

 of siphonophores or medusae. The long retractile claws on the last two, 

 three, or evdn four pairs of pereopods could stretch into a spoon-shaped 

 depression at the tip of the 6th segment, together with the seized tissue 

 of the host, which would ensure a firm attachment of the crustacean to 

 its "carrier". Their occurrence on large deepwater coelenterates enables 

 the less mobile lanceolids to reach larger sizes, up to 30-70 mm. 



Family lanceolidae includes five genera. 



KEY TO GENERA OF FAMILY LANCEOLIDAE 



1. Sixth segment of pereopods I narrows distally. Eyes compact or 

 absent. Pereopods V with spoon-shaped tips and retractile claws, 

 sometimes poorly developed 2. 



— Sixth segment of pereopods I enlarges distally. Eyes comprise indi- 

 vidual eye spots. Pereopods V without retractile claws 



5. Prolanceola Wolt. 



2. Mandibles with broad cutting edge and vefy small, sometimes 

 reduced to a tubercle, accessory plate 3. 



— Mandibles with narrow cutting edge and well-developed, almost 

 equally broad accessory plate 3. Megalanceola Pirl. 



3. Spoon-shaped formation on pereopods V-VII developed to some 

 50 extent but not swollen on rear side; claws 1/10-1/5 length of 6th 



segment. Palp of maxillae I at least equal in length to outer lobe . . 

 4. 



— Spoon-shaped formation on pereopods V-VII well developed, 

 swollen on rear side; claws 1/4-1/3 length of 6th segment. Palp of 



