8 
of the thread-shaped part of the tentacles takes place after the 
opening of the velar plate. 
Geographical distribution. 
Atlantic Ocean : 
Lat. 20° 39’ N., Long. 61° 48 ’ W. North of the Lesser An- 
tilles. June 4th 1920, 3 0u am. 2m ring-trawl, 300 m wire. “Dana”- 
Exped. stat. 850. — The type specimen. 
Lat. 36° 50’ N., Long. 21 0 W. Between the Azores and Ma¬ 
deira. Andrea 1872. — On two specimens of Hyalæa trispinosa. 
Only some stolons and a few polyps left. 
Lat. 2° 30’ N., Long. 24° W. Between Africa and South Ame¬ 
rica. Andrea 1863. — On four specimens of Hyalæa-trispinosa. 1) 
A fairly large colony with several polyps, most of which are placed 
on the ventral surface of the shell behind the shell mouth; hy- 
dranths with 0—5 tentacles. Stolons without polyps (broken off) in¬ 
side the lateral spines. Long stolons running backwards into the 
narrow hind part of the shell; no gonophores left. 2) Two young 
colonies, one with two polyps in the furrow behind the shell mouth, 
the other with one long stolon following the entire upper margin 
of the shell mouth, with two polyps. 3) A colony with two polyps, 
above the shell mouth. 4) One polyp, above the shell mouth. 
Indian Ocean. 
Lat. 31° S., Long. 47 0 E. — Lat. 32° S., Long. 43° 20’ E. 
South of Madagascar. Andrea 1870. — On one Hyalæa trispinosa , 
two polyps left, on the dorsal surface of the shell, near the left 
spine. 
The four localities are rather far distant from each other, which 
indicates that the species has a wide geographical distribution. 
Considering the large material of pteropods examined, the hydroid 
really appears to be somewhat rare; it is interesting to note, how- 
ever, that in one locality not less than four specimens of Hyalæa 
were infested. 
Vertical distribution. — The colony from the “Dana”- 
Expedition was taken about 100—150 m below the surface. The 
specimens of the old material have, probably, all been found near 
the surface. 
