FOSSOR1UM OF NEMAS 



401 



lateral lines near the middle of the tail on 

 both sexes. While there is no distinct bursa, 

 the cuticle is faintly thickened in the sub- 

 median region near the anus, possibly a very 

 rudimentary bursa. 



Habitat: Common among minute filamen- 

 tous algae on the surface of marine mollusks, 

 especially the snail Alectrion obsokta (Fig. 2). 

 Also found in sand on beaches, and in sand 

 in several feet of water off shore. Woods 

 Hole region, 1916 to 1927. There is good 

 reason to suppose it ranges both north and 

 south from Woods Hole along the Atlantic 

 Coast. It occurs in beach sand from near 

 Falmouth; and in clear white sand in five 

 feet of water in a cove at the entrance to 

 Buzzard's Bay; also at Waquoit, Mass., 

 among algae on the shell of the living snail, 

 Alectrion obsoleta (Nassa) ; and on the shells 

 of live snails from the Eel Pond at Woods 

 Hole. Its food seems always to be vegetable 

 matter, and in many cases consists entirely 

 of the contents of the cells of a microscopic 

 alga belonging to the genus Ralfsia (?). 



OUTWARD ACTING NEMIC "MANDIBLES" 



Fig. 3. Slight portion of the 

 algal growth from the snails shown 

 in Fig. 2, broken or dissected away. 

 Below is the shell of the mo Husk. 

 On it an "incrustation," orange in 

 color, consisting of an alga belong- 

 ing to the family Ralfsiae, prob- 

 ably to the genus Ralfsia. On this 

 incrustation there is a thick felt- 

 like growth, consisting of blue- 

 green and yellow-green algae. 

 Syringolaimus smarigdus feeds 

 upon the orange-colored alga, 

 which it can reach only by digging 

 through the green algal growth 

 above. 



The writer's study of the attitudes in 

 which the mouth parts became fixed led 

 to the conclusion that in Axonolaimus 

 and its relatives, as well as in a large 

 number of other nemas, the onchia (and 

 odontia) had an outward throw. If so, it 

 was an obvious deduction that these 

 organs were digging organs, for which 

 the word f ossor 2 seems indicated. This deduction led the writer long 

 ago to introduce into generic names of such nemas root words indi- 

 cating a digging function on the part of the mouth organs, as for 

 instance in the genus names Scaptrella, Diploscapter. 



It is, however, difficult to observe these organs in operation, and 

 hence of interest to record that such organs have been seen in action 

 in a Syringolaim (Fig. 1), and furthermore that S. smarigdus has been 

 observed under conditions constituting strong additional circum- 

 stantial evidence that these organs are verily digging organs. S. 



* F ossor (plural, fossores; collective, fossorium); a tool or organ used for digging, 

 usually existing in a plurality and acting symmetrically outward from a plane or axis. 

 Related to "fossorial" said of animals that dig. 



