I'EESIDENX .S ADDBESS. 107 



TuNicATA. — The Tuuicata of tlie deeper parts of the ocean are 

 few iu number, but interesting in character, and sometimes re- 

 markable for their size. 



MoLLTJScA. — Certain groups and genera of Mollusca are emi- 

 nently characteristic of depths of 500-2,000 fathoms. Among 

 Lamellibranchiata Pecten, Amussium, and Lima represent the 

 Ostreacea. The Mytilacea occur in the genera (Mbdiola lutea), 

 Idas, and Bacrydium. Arcacea are almost always found in some 

 forms of Nucula, Leda {Portlandia), MalleUa, Glomus, Area, or 

 Limopsis. The Lucinacea have many representatives in the genus 

 Axmus, and also in KelUa, KelUella, and Montacuta. Ahra puts 

 in an appearance for the Tellinacea ; and Lyonsia, and numerous 

 species of PeccioUa and JSfem-a for the Myacea. The class Soleno- 

 conchia is quite at home, and embraces Dentalium, Siphonoden- 

 talium, Entalina, and Cadulus. Of the class Oasteropoda we find 

 among Onychoglossa the genus Propilidium; among Rhaphidi- 

 glossa, numerous genera, especially Fissurisepta, Scissurella, 

 Trochus, Cyclostrema, Ganessa, and Sequenzia ; among Tsenio- 

 giossa, Cithna, Bunker ia, and Natica; among Ptenogiossa, 8ca- 

 laria and Aclis ; among Gymnoglossa, Eulhna and Odostomia ; 

 among Toxogiossa, Pleurotoma, Befrancia, and Taranis ; among 

 Rhachiglossa, Metzgeria and Trophon ; among Odontoglossa, Py- 

 rene and the subgenera of Fusus ; among Tectibranchiata, Utri- 

 culus and Scaphander. In the first famous dredging of the 

 ^Porcupine'' in 1869, Stat. 37, five Mollusca were found in 2,438 

 fathoms. These were the pretty little Mussel Bacrydium vitreum, 

 Moll, which I have dredged near the mouth of the Hardanger 

 Fiord in not more than 80 fathoms, Bentalium candidum, Amus- 

 sium fenestratum, and Ahra nitida. The last species is perhaps 

 better known to British Couchologists as Syndesmya intermedia, 

 and has an enormous range in,depth, from 3 to 2,435 fathoms. 



Bkachiopoda. — Of North Atlantic Brachiopods Terehratula 

 vitrea. Born, is known to descend to 1,456 fathoms; Terehratula 

 caput-serpentis, Linn., to 1,180 fathoms; Waldheimia tenera, Jeff., 

 to 1,450 fathoms; Atretia gnomon, Jeff., to 1,750 fathoms; and 

 Biscina Atlantica, King, to 2,425 fathoms. Terehratula Wyvillei, 



