zoology: marine invertebrates. 89 



Nahant headland as well as other parts of Massachusetts bay, dur- 

 ing the spring and summer months. Glava leptostyla occurs on the 

 rockweed in a number of places along the Nahant shore, and Bou- 

 gainvillia superciliaris is a not uncommon inhabitant of the deeper 

 tide-pools. Agassiz mentions the occurrence of Hydractinia poly- 

 cUna on the rocks in these tide-pools — a rather unusual habitat for 

 that species, which most commonly is to be found on shells inhab- 

 ited b}' hermit crabs. The following tubularians are also mentioned 

 by A. Agassiz' as having been found at Nahant : Eudendrium 

 tenue ; Rhizogeton fusiformis ; Syndictyon reticxdatum; Gemmaria 

 dadophora ; Pennaria tiarella ; Hyhocodon prolifer, and Tliamnoc- 

 nidia tenella. Among the campanularians, the genus Clytia is 

 represented in these tide-pools by C. intermedia, C. bicophora, G. 

 {Platypyxis) eylindrica, and C. {Orthopyxis) poterintn. The last 

 three of these species are common, the first has been recorded only 

 by A. Agassiz. According to him, the following species also 

 have been found : Eucope diaphana {=OheUa diaphana, Verrill) ; 

 E. attenuata (^0. geniculata, Hincks ; often on Laminaria in 

 tide-pools); E. polygona {:=0. polygona, Verriil) ; E . p>arasitica ; 

 E. pyriformis ; E. alternata ; E. {?) fusiformis; Obelia com- 

 missnralis ; Diphasia rosacea; Sertularia cupressina and Amphi- 

 trocJin cincta. 



As in most places along our shore, so here the two hardy species, 

 Sertularia ptcmila and Campanularia Jlexnosa {Lcwmedea am- 

 phora Ag.), are abundant on and under the rockweed which 

 fringes the pools. Various medusae often may be found in the 

 pools ; but the real fishing ground for these creatures is off East 

 point, where they always may be found in number. " At this spot 

 the sea actually swarms with life ; one cannot dip the net into the 

 water without bringing up Pleurobrachia, Bolina, Idyia, Melicertum, 

 etc., while the larger Zygodactyla and Aurelia float about the boat 

 in numbers."^ 



The attached medusa Lucernaria (Haliclystus) auricula is found 

 sometimes on the seaweed of the pools ; but its more normal habi- 

 tat seems to be among the eel-grass, to which it may be found 

 attached in many places along our shore. 



Sea anemones are abundant in most of the pools, where they 

 are shaded from the sunlight and sheltered from the strong waves. 



* North American Acalephs. 



» Agassiz, Elizabeth C. and Alexander. — Seaside studies In natural history, p. 86. 



