MUSEUM OF COMPARxiTIVE ZOOLOGY. 



EXPLANATION OF THE PLATES. 



a. Blastopore. 



ad. Interambulacrals. 



ad^, ad '2, ad^, ad*, ad^. Interambulacrals in sequence. 



am. Oral ambulacrais. 



am^, am", ain^, am*, am^. Anibulacral rafters in sequence. 



amd. Interambulacral ends of the oral ambulacrais. 



bn. Brachiolarian notch. 



c. Connectives. 



cbw. Circular blood-vessel. 



cw. Circular water tube. 



d^. First dorsal (radial). 



d\d^,d*,d'=,d^,d-. Dorsals. 



dc. Dorsocentral. 



c?f/i, rf(/2, <f(f3. Early formed body plates in radial lines. 



dl. Dorsolateral, or lateral dorsal. 



/. Feet. 



9' 9\ 9~' f> 5^. 9^- Genitals (basals). 



9^- Genital near the madreporic opening, through whicli the 



madreporic tube opens. 



j'. Intestine. 



^b- First interbrachial, or odontophore. 



ib"^ Second interbrachial. 



ibn. Interbrachial notch. 



''• Lateral region of the terminal. 



m, rn}, m-, m^. Marginals. 



mb. Madreporic body. 



mt. Madreporic tube 



0. Mouth. 



0^- CEsophagus. 



o™- Oral ambulacrais. 



I'd- Pedicellaria. 



sp- Spines. 



St. Stomach. 



s'c. Stone canal. 



t, 0, f-, t\ t*, t\ Terminals. 



'- *^- Terminal tentacle, or extremity of the medial water tube. 



"^- Unabsorbed region of the brachiolaria. 



