Letters from Agassiz on Temnechinus [Sea Urchin] of Crag, dredged off of Florida, and Salensia of Chalk. Makes reference to D'Archiac's research on Nummulites of India and similarities with Florida. Dredge depths given. Letters also on Glacial of America. On the death of his father, he writes to ask Lyell for any correspondence between him and his father, or reviews or publications, as he and his mother are compiling his father's biography. Final letter thanks Lyell for his contribution (Lyell has sent letters and information back) and details Agassiz's coping with the impact of his father's death.