8 DR. P. P. CARPENTER O^' THE SHELLS OF PANAMA. 



126. Triton chemnitzi> = Arijcbut:cinam nodosum, M. 580. These 

 shells are small and turreted. Those Prof. Adams marked " T. cin- 

 galatum. Lam., E. Indies," are much more like tlie Mazatlau shells. 



127. Triton const rictus^ Distortio c. The specimens of this 

 group from the Pacific Coast, from the Gulf of Mexico, and Iroai 

 the China Seas are very difficult to discriminate. 



128. Triton fusoides. This unique and very elegant shell can 

 scarcely be called a Triton, even of the Epidromus type. It may 

 ])er)iaps rank wifh Euthria, but is fjeculiar in possessing a distinct 

 anterior sinus, near the canal, like Rostellaria. 



129. 130, 131, 132*, 133, 134*, 135. Stent. 

 1!^6. Murex duhius=Muricidea duhia, M. 673. 



137. Murex erosus^Muricidea e. 



138. Murex radix = Phyllonotus r. The Professor's specimens 

 of this species are remarkably fine, more nearly resembling the Gulf 

 niyritus than the heavy stumpy shells usually seen. His youji^ 

 specimens are heavier, but more turreted, than the young nigritus. 

 The opercula appear to have fewer frills ; but such differences may 

 be due only to station. The specimens he marked ambiyuus (with- 

 out locality) belong to the typical nigritus. Phyllonotus radix and 

 nigritus graduate into each other almost as freely as the latter does 

 into anhiguus : v. M. 666. 



13!i. Murex rectirostris. This and kindred species run into each 

 other too closely, when adult, to speak with any confidence on so 

 young a specimen in bad condition. 



140. Murex recurvirostris. This specimen is also far too imper- 

 fect to affiliate: v. M. 665. 



141. Murex regius= Phyllonotus r., M. 670. 



142. Murex salebrosus= Vitularia «., M. 612. The curious group 

 of Muricoid Purpurids culminates on the West .\merican shores. It 

 is represented in the north temperate regions by Cerastoma, on the 

 warmer shores by Chorus, and in the tropical regions by Vitularia. 

 The Lower Californian Murex helcheri, Hds., belongs to the group. 

 Dr. Alcock (who has succeeded the late Capt. Brown as Curator of 

 the Manchester Natural History Museum) has pointed out very well- 

 marked physiological distinctions between the two families, which 

 are coordinate with the diiferences in the opercula. 



* Dr. Gray (Guide to MoUusca, pp. 39, 42) leaves the round-variced Ranellids, 

 as ApoUon, in the Tritonida, " operc. annular, nucleus subapieal, within the 

 apex ;" but removes the sharp-variced species, as Ranella, to the Cassididee, and 

 figures the operculum like Bezoardica, " half-ovate, nucleus central, lateral, in- 

 ternal." The operculum of R. cmlata, No. 132, is almost identical with Murex, 

 and the shell accords with Apollon; but R. nitida. No. 134, which has very sharp 

 varices, has its operculum widely removed from Beaoardica. It is closely related 

 to that of Cerastoma, Rhizocheilm, and some of the Ocinebrte; nucleus near the 

 anterior end of the labrum ; labral portions of the annular layers eroded ; scar as 

 iu Purpurids, vmUi about thiee roughly angular ridges uf growth. 



182 



