48 



PROF. P. M. DUNCAN AND ME. "W. P. S LADEN ON THE 



In naming these latter creature.s specifically, I have done so 

 with considerable hesitation, as it must be confessed my know- 

 ledge of these groups is much too limited to warrant my speaking 

 with any great degree of certaiaty. 



Thus ends my notes on Liimpenus lampetriformis ; and I trust 

 its habits and history have not been left shrouded altogether in 

 the darkness in which I found them. 



Since writing the foregoing I got, on June 5th, five more 

 specimens of Lumpenus, one of them, a female, carrying spawn, 

 which w^ould have been deposited within a fortnight or three 

 weeks at latest. This brings my supposition relative to the 

 time of spawning to be pretty nearly correct, viz. the end of July 

 or beginning of August. 



The longest specimen mentioned by CoUett was 412 millim. ; 

 my longest one was 12| inches. 



On the Anatomy of the Perignathic Grirdle and of other Parts 

 of the Test of Biscoidea cylindrical Lamarck, sp. By Prof. 

 P. Martin Duncan, P.E.S., and W. Percy Sladen, P.G.S., 

 Sec. L.S. 



[Eeacl ITtli June, 1886.] 



DiscoiDEA CTLiNDBiCA, the Galcrites cylindricus of Lamarck, is 

 one of the commonest of the Echinoidea from the Upper Creta- 

 ceous strata; and its shape and internal casts in flint are familiar 

 to all geologists. Desor, Wright, and Cotteau have described 

 the sj)ecies; and the last-named palaeontologist has enlarged the 

 generic diagnosis of Discoidea in consequence of some morpho- 

 logical details which had been elaborated by himself and some 

 previous observers, especially E. Eorbes and Loven. 



Discoidea cylindrica has five basal plates in its apical system, 

 and the fifth or the posterior one is not perforated for a genital 

 duct. But the palaeontologists just mentioned found a perforated 

 fifth basal in species which they felt bound to classify in the 

 genus Discoidea. Loven, speculating on this association of im- 

 perforate and perforate basals in difi'erent species of the same 

 genus, considered it an instance of evolution during time. 

 Cotteau extended the generic diagnosis, and added to that of 

 Desor the following : — "Apical system compact, subpentagonal, 



