ZOOLOGY AND BOTANY, MICBOSCOPY, ETC. 
165 
which may be called anodoiit, prionodont, and orthodont. The last, in 
which the cardinal margin has become longitudinally plicate, hardly 
exists ; in nearly all forms traces of the prionodont characters are mingled 
with it. For those forms in which the archaic anodontism still persists 
as the characteristic of chief importance, though frequently modified by 
special mechanical contrivances which to a certain extent mark the type, 
the term of Anomalodesmacea is proposed. Forms in which transverse 
plication of the hinge is the chief characteristic may be called the Priono- 
desmacea, while those which have the various types of hinge harmoniously 
combined are called the Teleodesmacea. Thus these groups may be 
regarded as orders, and each, as it now exists, contains archaic and 
modern specialized types; each has a tendency towards an ideal of 
fitness to the environment which results in a certain parallelism of minor 
characters common to minor groups in each of the three orders. In each 
certain members show affiliations with members of the other orders, and 
in each there are certain groups which represent a relatively modern 
specialization carried so far as to be quite peculiar. 
The suborders of the Anomalodesmacea are : — 1. Solenomyacea ; 
2. Anatinacea; 3. Myacea ; 4. Eusiphonacea ; and 5. Adesmacea. Of 
the Prionodesmacea : — 1. Nuculacea ; 2. Arcacea ; 3. Naiadacea ; 4. Tri- 
goniacea ; 5. Mytilacea ; 6. Pectinacea ; 7. Anomiacea ; and 8. Ostracea. 
Of the Teleodesmacea ; — 1. Tellinacea ; 2. Solenacea ; 3. Mactracea ; 
4. Carditacea ; 5. Cardiacea ; 6. Chamacea ; 7. Trinacreacea ; 8. Lepto- 
nacea(?); 9. Lucinacea ; 10. Isocardiacea (?) ; 11. Veneracea. The 
position of the Rudistes is uncertain, but they may be a specially modi- 
fied and extraordinary branch of the Chamacea. 
The author gives the reasons for preferring his views and classifi- 
cation to those of the late Dr. Neumayr, with whom, however, he is in 
agreement as regards many important points. 
Fourth Pallial Orifice of some Lamellibranchs.^ — Prof. P. Pelseneer 
finds that, when there are four openings in the mantle of a Lamellibianch, 
there is a relation between the fourth orifice and that of the byssogenous 
apparatus. In some forms in which the mantle is a good deal closed, 
and the foot as a locomotor organ reduced, while the byssus is con- 
siderably developed, the primitive pedal orifice is divided into two 
secondary orifices ; the anterior of these remains a pedal orifice, the 
other is only used for the passage of byssus ; such an arrangement was 
observed in Lyonsia. In Lamellibranchs with four pores, which are pro- 
bably the descendants of forms organized like Lyonsia, the byssogenous 
apparatus is atrophied and the pallial orifice for the byssus has followed 
the retrogression ; it is reduced to a sn)all hole which is generally found 
at the point occupied by the byssal orifice of Lyonsia, and opposite the 
spot where the byssogenous apparatus is normally developed in Lamelli- 
branchs. This fourth orifice may then be considered as the remnant of 
the opening which served exclusively for the passage of the byssus. 
Comptes Rendus, cx. (1890) pp. 154-6. 
