NOTES ON PLYMOUTH HYDROIDS. ZI 



the other. In their incipient stages it is difficult to tell the 

 difference between sarcostyles and gonophores, and they 

 make their appearance at about the same period in the devel- 

 opment of the corbulas. 



Aglaophenia helleri Marktanner-Turneretscher. 1 This 

 is the form collected by Mr. Allen from Eddystone Rocks, 

 and mentioned by him on page 49, Volume iv, No. 1, of this 

 Journal. This being the first record of A. helleri on British 

 shores, the following description is given for the benefit of 

 those who may not have access to the original — 



Trofihosome. Colony unbranched, attaining a height of three- 

 quarters of an inch. Stem monosiphonic, divided bv very 

 deep nodes into short internodes, each bearing a hydrocladium 

 springing from its anterolateral aspect. Hydrocladia alter- 

 nate, closely-set, divided into internodes each bearing a hydro- 

 theca, and partly divided by two imperfect transverse septa. 

 Nodes very distinct. Hydrothecae obconic, about as deep as 

 the aperture is wide. Marginal teeth nine, unequal in size* 

 the anterior one often being slightly" incurved, and rather 

 longer and more pointed than the others; the second and 

 fourth teeth, counting from behind, are larger than the first 

 and third. There is no apparent intrathecal ridge. Supra- 

 calycine nematophores rather small, stout, reaching to the 

 level of the hydrothecal margin; the mesial nematophore 

 springs from just below the margin of the hydrotheca, and 

 projects straight upward and outward, its truncated end reach- 

 ing to the level of the longest marginal teeth. There are two 

 modified nematophores on each hydrocladium near its base. 



Gonosome. (Description from Naples specimen.) Corbula 

 thick and short, with the leaves or ribs more closely soldered 

 together than in other small British species. Ribs six on each 

 side, with a row of nematophores on their distal edges. 



Habitat. Found growing on thick roots of marine plants 

 taken from Eddystone Rocks. 



Distribution. Naples and Rovigno (Marktanner-Turn- 

 eretscher), and Plymouth, England. 



x Die Hydroiden des K. K. Naturhistorischen Hofinuseiims, Vienna, [890, p. 

 271, plate vii. 



