I'ATKLI.A. 83 



spatula. P. athletica F. & II. is a syiionym. This forin is tliicker 

 and iiioi-e coarsely sculptured than the var. aspersa Lam. 



P. o.ERULEA Linne. PI. 10, figs. 7-12. 



Shell depressed, thin, spreading, usually more or less distinctly 6 

 or 7 angled ; riblets rather fine and notably unequal. 



Mediterranean and Adriatic Seas; Madeira; Azores; Canaries. 



P. cverulea L., I. c, p. 1259.— Hanley, Sh. of L., p. 421.— Phil., 

 Enum. Moll. Sicil. i, p. 109, t. 7, f. 5.— Reeve, Conch. Icon., f. 28. 

 —Hidalgo, Mol. Mar. Esp., t. 50, f. 5, 6 ; t. 51, f. 1, 2.— Buq. 

 Dautz. & DoLLF., Moll. Mar. Rouss., p. 471, t. 58, f. 1-7.— P. 

 fragilis Phil., Enura. i, p. 40, t. 7, f. Q.—-P. subplana P. & M., 

 Galerie de Douai, i, p. 524, t. 37, f. 3, 4. — P. coirulea v. subplana 

 Bttq. Dautz. & Dollf., Moll. Rouss., p. 473. — P. tarentina Lam., 

 not V. Salis. — P. scutellaris Blainville, jiot Lam. 



P. aspera Lam., An. s. Vert, vi, p. 327. — P. bonnardi Rve., not 

 Payr. 



P. tarentina v. Salis, Reise ins Koenig. Neapel, p. 359, t. 6, f. 2. — 

 P. honnardi Payr., Moll, de Corse, p. 89, t. 3, f. 9-11. 



P. crenata Gmel., Syst., p. 3706.— Orb., Moll. Canaries, p. 97, t. 

 7, f. 6-8. — Drouet, Moll. Mar. Agores, p. 40. 



Separated from P. vidgata mainly on account of its more 

 expanded, depressed, generally thinner shell and more southern 

 range. I am wholly inclined to believe that the line of separation 

 is artificial, and that the two species vulgata and ccerulea fade into 

 one another. 



The variations of the genuine ccerulea are numerous including the 

 folloAving forms: 



Yorm. fragilis Phil. Shell thin, the radiating strise very fine. 



Form intermedia B. D. & D. Intermediate between the regu- 

 larly oval and the polygonal forms. 



Form adspersa B. D. & D. Dotted with white on a greenish- 

 gray ground. 



Form subplana Pot. & Mich. (figs. 7, 8). Large, thin, pentagonal, 

 the apex quite anterior. This is P. scutellaris of Blainville, Reeve, 

 and others. As mutations under it rank form stellata B. D. & D., 

 having the angles prolonged, star-like ; form cognata B. D. & D., 

 having the pentagonal form of subplana and the rugose sculpture of 

 aspera. 



