NEED TO CLASSIFY—BATTEN SrA 
Thus, up to 1956, stood the classification of the primitive forms of 
gastropods—a far cry from the first classification that had viewed all 
the limpets as members of one family. 
Now, looking at the fossil record, we can make another observa- 
tion. The primitive monoplacophorans were not a successful group 
of animals: they apparently became extinct about 280 million years 
ago—probably giving way to the more advanced limpets, which could 
more successfully adapt to the environment of that time. But about 
8 years ago, during the expedition of the Danish vessel Galathea, sev- 
eral tiny cap-shaped shells were brought to the surface by the deep-sea 
dredging operations. The natural first impression was that they were 
limpets, because no other group of cap-shaped shells were known to 
be extant. Upon careful examination in the laboratory, however, 
some sharp differences were noted between these forms and the usual 
gastropods adapted for rock-clinging environment. This new form, 
duly described and named Neopilina galathaea, was presented to the 
astounded scientific world early in 1957. Others have been found since 
then. For here was a living monoplacophoran, previously thought to 
be extinct for 280 million years! (See fig. 12 and pl. 1.) MNeopilina, 
with its eight distinct muscles and bilateral symmetry—mouth and 
anus at opposite ends of its body—is the very organism hypothetically 
constructed by the paleontologists 5 years before. 
Many of the characters of Neopilina predicted by the paleontologists 
were found: several other characters that could not have been pre- 
dicted were also present. These additional characteristics are bring- 
ing even further changes in classification. One major discovery is the 
presence in Veopilina of what appears to be body-cavity segmentation, 
and a separate gill for each of the paired muscles. Segmentation of 
the body cavity is considered by zoologists to be a primitive char- 
acteristic. Such segmentation is shared by several very different 
phyla, including the worms and the arthropods (that great group 
which includes such diverse forms as lobsters, spiders, and insects). 
One suspects that there will be a strong temptation to revise classi- 
fication in a manner which will relate some of these diverse forms 
more closely than is the case at present. 
In our own task of unraveling the complex relationships between 
various primitive mollusks, the discovery of Veopzlina has sent the 
paleontologists back to further study of their collections. Perhaps 
some minor feature, overlooked before, will now have great signif- 
icance. Already some of the rather vague muscle scars of fossils that 
had been placed in other gastropod families indicate that these belong, 
instead, among the monoplacophorans. 
The search is far from completed; it will take several years for all 
of us to understand and reevaluate our data. So far, we know much 
more about how the gastropods and other mollusks came to be and, 
