OCULAR AND GENITAL PLATES. 



117 



Of the first family, the Temnopleuridae, 400 specimens inchiding 15 species have been 

 studied as Hsted in the table, p. 159. The Cretaceous Glyphocyphus radiatus has very low 

 genitals and oculars, and the latter are all insert in the seven specimens seen. The Recent 

 Temnopleurus reevesii shows a strong tendency for ocular I to be insert, and this with other 

 cases indicates that this is the first plate to become insert in this family as in the Echinidae. 

 All the other species Tiave all oculars exsert with rare exception. Microcyphus maculatus (139 

 specimens) in one case has oculars I, V insert, the only case seen in the family, and two aberrants 

 were found, one with ocular IV insert and one with II insert, both very rare occurrences in 

 Echini as a whole. Mr. Agassiz (1873) and Dr. Mortensen (1904, p. 63) note that one or more 

 ocular plates may be insert in species of this family, but in Recent species they are apparently 

 exceptional characters, and, as a whole, the family from present evidence is characterized by 

 oculars all exsert. 



In the family of the Echinidae I have had the opportunity to examine a large number of 



in 



III 



nr 



115a 



Text-fiu.s. 11.5-117. — Ocular plate arrangcmcntr in .species of Echinus. 



115. Echinus affinis Mortensen. Off east coast of United States, 1,022-1,10(5 fatlioms. U. S. Nat. Mus. Coll., 

 11,851. X 3. All oculars exsert, extra genital pores, arntjulacral ]ilates composed of two elements dorsally, and are simple 

 primaries next the ocular. Plates of periproct numerous and very small excepting the suranal opposite genital 3 (pp. 171, 

 176). 



115a. Same species and locality. R. T. J. Coll., 891. X 3. Ambulacra! plates of two elements each, extending 

 down to Ihe mid-zone, below which all have three elements (p. 216). 



115b. The same. R. T. J. Coll., 892. X 3. No ambulacra! plates with two elements each. 



116. Echinus esculentus Linne. English Channel. Diam. 103 mm. R. T. J. Coll., 723. X 2. All oculars exsert, 

 typical character. 



117. The s.ame. Plymouth, England. Diam. 94 mm. R, T, J. Coll., 764. X 2. Ocular 1 insert, a progressive 

 variant. 



