HYDROIDS OF THE WOODS HOLE REGION. 
369 
HYDROID MEDUSAE FOUND IN THE WOODS HOLE REGION. 
A monographic account of the medusae is in course of preparation by an eminent 
authority, and the present writer therefore does not desire to discuss the medusae in 
a systematic way, but hopes that the key herewith presented will be of service in 
identifying the medusae known to occur in the region. No attempt has been made 
to describe new species or to define families, genera, or other groups. The classifi- 
cation conforms, so far as possible, to the plan of the preceding part of this work 
when the hydroid form is known. Otherwise the names are the same as those found 
in Alexander Agassiz’s work, North American Acalephae. Almost all of the illustra- 
tions are from specimens taken at Woods Hole and Newport, and sketched by the 
author. 
Key for the identification of the Hydroid medusae found in the Woods Hole region. 
Otocysts never present. 
A. Ovaries attached to the proboscis walls and never found along the radial canals. 
a. Radial canals 4 unbranched. 
b. A single conspicuous marginal tentacle. Others, if present, much smaller. 
c. Proboscis not more than one-half length of bell cavity Euphysa virgulata. 
c'. Proboscis more than one-half length of bell cavity. 
d. A single greatly enlarged tentacle from which secondary medusee arise Ihjbocodon prolifer. 
d'. One large and 3 much smaller tentacles. No secondary meduste Corymorpha pendula. 
b' . Two conspicuous marginal tentacles. Others, if present, much smaller. 
c. Bell with a distinct apical projection. 
d. Apical projection a lengthened cone Stomotoca apicata. 
d'. Apical projection dome-shaped. Tentacles bearing stalked nematoeyst batteries. . Gemmaria eladophora. 
c'. Bell evenly rounded, without apical projection. 
d. Tentacles bearing stalked batteries of nematocysts Corynitis agassizii. 
d'. Tentacles normal Perigonimus jonesii. 
b". Four tentacles of approximately equal length. 
c. Proboscis and tentacles very long and slender. 
d. Bell outline subspherical Coryne mirabilis. 
d'. Bell outline subconical Dipurena conica. 
c'. Proboscis short, not reaching bell opening. 
d. Tentacles tightly coiled. Bell with 8 meridional lines of lasso cells Ectoplcura ochracea. 
d'. Tentacles rudimentary. No lines of lasso cells Pennaria tiarella. 
d". Tentacles functional. Radial canals very broad Hydrichthys minis. 
b"". Eight tentacles of approximately equal length. 
c. Tentacles strong, functional. Proboscis bearing secondary medusse Dysmorphosa fulgurans. 
e'. Tentacles rudimentary. No secondary medusai Slylactis hooperi. 
b""'. Tentacles more than .8, of approximately equal size when full grown, and disposed at regular intervals. 
c. A large globular or subconical process on apex of bell Turris vesicaria. 
c'. Bell evenly rounded above Turritopsis nutricula. 
b""". Tentacles in groups or bunches. 
c. Four clusters of tentacles. 
d. Proboscis small and slender. 
e. A pair of erect clavate tentacles in each group Ncmopsis baehei. 
e'. Tentacles much alike Bougainvillia carolincnsis. 
d'. Proboscis large and broad Bougainvillia superciliaris. 
c' . Eight clusters of marginal tentacles Lizzia grata. 
a'. Radial canals 4, branched at their distal ends Willia ornata. 
a". Radial canals many, bell cup-shaped Orcliistoma tentaculata. 
A'. Ovaries attached to the radial canals, often also to the proboscis. Otocysts usually present. 
a. Radial canals 4. 
b. Marginal tentacles 4, sometimes with lateral cirri. 
c. Proboscis very long, reaching far beyond the velum. 
d. A swelling at base of each tentacle Eutima mira. 
d' . No swelling at bases of tentacles : Eutima limpida. 
c'. Proboscis short. Bell deep. 
d. Tentacles with lateral cirri. 
e. Club-shaped appendages between bases of tentacles Hcbella calcarata (juv.). 
e'. No club-shaped appendages. 
/. Two otocysts between bases of adjacent tentacles Eucheilota ventricularis. 
f . Three otocysts between bases of adjacent tentacles Eucheilota duodecimalis. 
d'. Tentacles without lateral cirri Clytia bicophora (juv.). 
Clytia noliformis (juv.). 
F. C. B. 1899—24 
