APPENDIX. 173 



24. PAGE 28. Virgularia is so named from its rod-like form ; vira, 

 a rod. V. mirabilis is found off the English coast. 



25. PAGE 30. Ophiura and Asterias. These are genera of the sea- 

 stars, or star-fishes long so called ; the former so named on account of 

 the resemblance to snakes in its arms. 



26. PAGE 30. Ophiothrix fragilis, Amphiura belli, and Ophiocantha 

 spinulosa. 



27. PAGE 31. Ophiocnida olivacca and Ophiocantha bidentata. 



28. PAGE 31. Brisinga elegans. 



29. PAGE 32. Astrophyton. There are several species of this star- 

 fish, but each found in deep water. They are curiously circumscribed in 

 locality. In one place off Cape Cod they are dredged, but in no other 

 place, excepting farther south. Their name, basket-fish, is from their 

 numerous intwined arms, resembling basket-work. 



30. PAGE 37. Serpula. A genus of the group Annelida. 



31. PAGE 37. Neiridce and Eunicedce. Genera of the group Annelida. 



32. PAGE 37. Polynoidce, Scyllidce, Chcetopteridce, and Polycirus. 



33. PAGE 38. Chcetopterus norvegicus. 



34. PAGE 39. Harmcethe imbracta emits a bright greenish light when 

 disturbed, the luminosity evidently proceeding from the point of attach- 

 ment of each dorsal scale. 



35. PAGE 40. Pholas. A clam-like mollusk. Several species are 

 found on Nahant beaches. ' P. dactylus is a European form. The genus 

 Zirphcea is found from New England to Great Britain. All are more or 

 less borers. A small species bores in hard mud on the Nahant beaches. 

 Others are known to bore into hard wood and into stone. 



Pholas dactylus will be seen to have photogenic or light-emitting struc- 

 tures and substances almost concealed in the tissues of the animal. The 

 light-emitting portions are, according to Panceri, "two parallel cords 

 containing an opaque white matter extending down the anterior siphon, 

 two very small spots at its entrance, and finally an arched cord corre- 

 sponding to the superior edge of the mantle, reaching to the middle 

 near the valves. The white color of the cords, which stand out in relief, 

 distinguishes them; and, although they are only elevations of the sub- 

 cuticular tissue, they contain special cells, or rather epithelium, which 

 produces the phosphorescent matter. The whole surface of the Pholas 



