400 MOLLUSKS OF THE GALAPAGOS STEARNS. 



was attiU'liod, wliother resulting in \\w i)iiicliiii<;- tojicther or compression 

 of the sidos, etc., the cupliUe i)roccss is uiki fleeted .so far as relates to 

 the proportion of the same that is attached to the inner surface. Car- 

 penter's jxrf/wrffMwj, to which in manuscript he gave also the name 

 fJcicctti {V. S. ]Mns,, No. r>(>LM»4), tignicd in Kccvc's JMonouraph in jd, v, 

 11, llrt, exhibits the characters and extent or proportion of the cup that 

 is fixed to the side. 



A careful examiinition of one hundied an<l thirty-four exani])les in- 

 cluded in thirty-two lots from thirteen localities between Lower Califor- 

 nia, in the north, and ]*ayta, Pern, in the south, discovered no connect- 

 ing links between the usual foiui of the cup, as seen in the species of the 

 imbricated group, and the triangular cup o( the ^xrfinat ton, scrratum, 

 etc., forms I have named. Besides the above example oi pectinatHm, 

 which was collected at Mazatlan, the Museum series contains two from 

 the " Gulf of California" (No. 0(>2;>!)), which, on previous and hasty 

 identifleation, were wrongly determii\ed as "fm6n'ca<»<m var.," and a 

 fourth from Panama; the exterior sculpture is also persistent and 

 characteristic, easily separable from the others of the inihricatcd 

 group. Of the one hundred and ninety-four examples of the sphwfic 

 form from nineteen localities between San Pedro, California, in the 

 north, to Payta, Peru, in the south, and the (Jalapagos, in the >s^ational 

 Museum, not one example occurs, whatever nuiy be its shape, compressed 

 ori)inche(l, conical or flattened, wherein the internal cup is attaciied as 

 in 2^('<fi nation J etc.; neither have 1 observed in the course of going over 

 the two groups imhricatum and spinosion any dilliculty in separating 

 them or any reason for uniting them by reason of the occurrence of 

 varietal forms Avherein the charaeters are too indefinite for satisfactory 

 determination. 



The foregoing is printed as written nearly two years ago. Recently, 

 in relation to the Tertiary fossils of Florida,* Dr. Dall has referred to 

 this character of the attachment of the cuj), and he assigns certain 

 forms, wherein the cup is adherent, to J>ispot(va (Say) Conrad. 



Dispot(ra as a section or subgenus of Crucibuluni will therefore hi- 

 vhxde pciiinatitm + Jvicetti, scrratum, concamcratum, striatum, auritum, 

 and aordidum. 



In this portion of his paper Dr. Dall remarks, " the siiecies of both 

 groups [Crncihidum .v. s.; and JUspofa'a] have been very greatly over- 

 stated by naturalists Avho have assumed the constancy of the surface 

 characters or those due to station." Farther on he says, " the Pacific 

 imbricatiim, except for the link furnished by the. fossils, is (|uit(^ dis- 

 tinct from its near relative, C. spinosnni, but in the Pliocene fossils the 

 intermediate forms are more numerous, and t hire the two can hardly 

 be regarded as distinct species." 



Transactions "Wapicr Institute. Phila., Vol. m, jiart ii, Pec. 1892. 



