INVESTIGATOR SIGARIUS, A GEPHYREAN WORM 



HITHERTO UNDESCRIBED, THE TYPE 



OF A NEW ORDER. 



By F. H. Stewart, M.^., D.Sc, M.B., C apt., I. M.S., Surgeon Naturalist, 



Marine Survey of India. 



Specimens of the animal for which the name Investigator sicarius is proposed 

 have been taken on two occasions by the R.I. M.S. " Investigator." The first occa- 

 sion was in 1900 at station No. 268, 7° 36' N. 78° E., in the Gulf of Manaar, where 

 eight specimens were obtained at a depth of 595 fathoms from a bottom of green 

 mud and sand. The second occasion was in 1908 at station No. 378, 19° 32' N. 

 92° 41' E. off Arakan at a depth of 250 fathoms on a bottom of soft green mud. 

 Only one specimen was obtained at the latter station. 



On being examined during the summer of 1908 in Calcutta the specimens from 

 station No. 268 were found to be well preserved for examination of the exterior but to 

 be so hardened by age and alcohol as to be useless for study by sections. The speci- 

 men from station No. 378, however, which, after being fixed with mercury and passed 

 through absolute alcohol was preserved in cedar- wood oil, was in excellent condition 

 for this purpose and a complete series of sections was obtained. 



INVESTIGATOR SICARIUS, gen. nov., sp. nov. (Plate xxi.) 

 Gênerai, appearance. (PI. xxi, fig. i.) 



The body divides itself naturally into trunk, neck and head. The trunk is 

 sausage-shaped, narrowing in front fairly abruptly to the neck which is approximately 

 one-and-a-half times the length of the trunk and bears the globular head. There are 

 no tentacles. The mouth is slit-like, situated on a diamond-shaped area of tough- 

 looking skin. At the margin of this area is a circle of minute black dots, and behind 

 it the head carries several circles of simple short spicules. 



The skin of the neck and body is regularly covered with glassy chitinous spines , 

 needle-shaped on the anterior portion of the neck, broadly lanceolate on the trunk 

 (pi. xxi, fig. 2). (In fig. I the artist has represented the spines as not covering the 

 whole of the body. This is due to their translucency which causes them to be visible 

 only at certain angles.) 



The hinder end of the body is formed by a hardened, flatly conical shield separ- 

 ated from the rest of the body by a shallow groove. The spines at the edge of the 



