276 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
metapleura pass equally into the rostral fin in front ; an intertentacular 
membrane is present between the ventral buccal cirri ; the buccal cirri 
are plain ; and lastly, there is a pair of very short postatrial caeca. 
In addition to the length of the body and the number of myotomes,. 
an important specific feature of Asymmetron caudatum is the rostral 
fin, which is marked oft* from the dorsal fin by a constriction. There 
is a distinct caudal fin extending to the posterior extremity. 
INVERTEBRATA. 
Hard Parts of Invertebrata.* — Mr. L. P. Gratacap, in an essay on 
“ fossilisation,” gives the following summary in regard to the hard parts 
of Invertebrates. The calcareous Foraminifers are composed of calcite, 
with some aragonite. True corals are composed almost entirely of 
aragonite. Alcyonarians contain for the most part calcite, with small 
amounts of aragonite and phosphate of lime. Echinoderma and many 
Annelids have their tests or tubes composed of calcite. Crustacean 
shells contain varying intermixtures of calcite and phosphate of lime. 
Bryozoa have cases composed of a mixture of calcite and aragonite. 
Brachiopods have shells of calcite and some phosphate, the latter almost 
restricted to the Inarticulata. In some bivalves the shells are wholly 
composed of aragonite ; in oysters and scallops, of calcite ; in Mytilus 
and Pinna, the outer layer is calcite, the inner aragonite. 
New Discoveries in the Mammoth Cave.f— Dr. E. Ellsworth Call 
has made some additions to the list of forty or so species which Dr. 
Packard described in his monograph in 1889. Without exception, the 
seven new forms are very minute, which explains their late appearance 
in the faunistic list of this much-studied cave. There are two new 
Thysanura, Entomobrya cavicola Banks, and Smynthurus mammoutliia 
Banks ; a new Psocid, Dorypteryx hageni Banks ; two new Acarina, 
Bhagidia cavicola Banks, and Linopodes mammouthia Banks ; a new 
Dipteron, Limosina stygia Coquillet ; and a new Gasteropod, Corychium 
stygium. Some new fungi were also found, e.g. Coprinus micaceus. 
Distribution of Marine Organisms.^ — Dr. A. E. Ortmann criticises 
a recent lecture by Dr. John Murray. (1) Ortmann denies the great 
resemblance between Arctic and Antarctic organisms ; (2) he points out 
that pelagic larvre are not absent from the cold polar waters ; (3) he main- 
tains that the true limitation of life-regions in the sea is according to 
conditions of illumination, and not by the mud-line or the like ; (4) 
he notes that the deep-sea fauna does include some very ancient types, 
like the Eryonidea among Decapods. 
Mollusca. 
Pulsations of the Heart in Molluscs. § — Mr. F. C. Baker has ex- 
amined 39 species of Bivalves and Gasteropods in reference to the 
pulsations of the heart. In some species it is very constant, in others 
* Amer. Nat., xxxi. (1897) pp. 285-93. 
t Tom. cit., pp. 377-92 (2 pis.), 
t Zool. Jahrb. (Abth. Syst.), x. (1897) pp. 217-8. 
§ Journ. Cincinnati Soc. Nat. Hist., xix. (1897) pp. 73-8. 
