Dr. Philippi on Pandorina coruscans. 295 



theless the margin projects directly before the vertex of the 

 right shell in the form of a little tooth (see fig. 3.). The ca- 

 vity for the ligament runs veiy obliquely backwards and is 

 perfectly linear. To my great surprise^ I found in my three 

 young specimens^ instead of the ligament, a bone, as in Osteo- 

 desma and others, of an elongated nearly pentagonal form, 

 with the apex directed anteriorly, the slightly hollowed basis 

 posteriorly, and moderately gibbous on the ventral side*. 



The animal of Pandorina has, according to a drawing com- 

 municated to me by Sr. Scacchi, two short slightly project- 

 ing siphons, with fringes at the margin, and a long compressed 

 and narrow foot, the situation of which proves that at least a 

 third part of the mantle anteriorly is split. 



I had found this shell in a fossil state in Sicily, and named 

 it Pandora ? cequivalvis in my ^ Enumeratio Molluscorum Sici- 

 liae,^ and I also noticed the resemblance and difference be- 

 tween it and Pandora as far as they were to be seen on the 

 fossil specimens. The principal differences in the shell are as 

 follows: 1. The right half is perfectly flat in Pa/ic^or«, in Paw- 

 dorina only a little less vaulted. 2. Pandora has teeth on 

 the hinge. Lamarck^s statement in ^ Hist. Nat. des Anim. 

 sans Vert.^ is not good ; on the contrary, that of Deshayes in 

 the second edition of the same work is excellent : they consist, 

 on the left shell, in a front tooth (which in those Pandorce that 

 I have at hand to compare is perfectly flat), and a deep cavity 

 between it and the ligament, into which fits a tooth of the 

 right flat shell. In Pandorina every trace of a tooth has dis- 

 appeared on the left shell, and on the right one only an ex- 

 ceedingly slight analogue to it exists in the projection of the 

 margin. 3. Pandora has quite simply an internal ligament. 

 I must however remark, that Pandora appears to me to pos- 

 sess also a second ligament, namely, immediately at the mar- 

 gin, fig. 5 «; fig. b. is the usual one. 4. Pandora has a per- 

 fectly simple muscular impression, whilst in Pandorina only a 



* Sr. Scacchi remarks, 'Eniim.,'p. 6. Note on Thracia, "in utraque 

 specie reperimus ossiculum mobile ad cardinem, quum specimina juniora 

 observavimus ; at in adultioribus sen majoribus etiam cum mollusco perqui- 

 sitis, illud nunquam invenimus. Miramur sane ossiculum illud adolescento 

 conchylio evanescere; sed sic observatio pluries repetita nos cogit opinari, 

 neque inspectio testarum suspicari permittit, specimina majora diversas eon- 

 stituere species." May not this also be the case with Pandorina l 



