218 



SCIENCE. 



[N. S. Vol. XIX. No. 475. 



septal stage to modern corals and aetinians, 

 but later developing in an altogether char- 

 acteristic manner. Of modern forms they 

 are most closely allied to the zoanthids, 

 ■which are without any true skeleton; in 

 these the growth of the mesenteries takes 

 place in a manner comparable to that of 

 the septa in the extinct forms, though pro- 

 ceeding in only two of the six primary 

 chambers. 



Demonstration of Preparations made dur- 

 ing a Study of the Life-history of the - 

 Cestode Crossohothrium laciniatum {Lin- 

 ton) : W. C. Curtis, University of Mis- 

 souri. 

 *The Types of Limb Structure in the Tri- 

 assic Ichthyosaurs: John C. Mereiam, 

 Berkeley, California. To be printed in 

 American Journal of Science. 

 The limb structure in the Triassic ich- 

 thyosaurs shows generally a much stronger 

 resemblance to the type of extremity found 

 in the primitive shore forms of the rep- 

 tilia than is seen in the Jurassic forms. 

 The limbs of Triassic ichthyosaurs show as 

 great a degree of differentiation, as is found 

 in the later types. Two fairly definite 

 lines of evolution are noticeable in the 

 paddle structure of the lehthyosauria, one 

 leading to the broad-paddled Latipinnati, 

 the other leading to the Californian 

 Triassic genera and to the narrow-paddled 

 Longipinnati. 



*A New Group of Marine Reptiles from- 

 the Upper Triassic of California: John 

 C. Merriam, Berkeley, California. To 

 be printed in 'Publications' of the Uni- 

 versity of California. 

 Marine saurians with abbreviated limbs 

 and slender, elongated snout. External 

 nares median. Temporal arcades slender. 

 Dentition heterodont, posterior teeth flat, 

 anterior teeth slender, conical. Elongated 

 vomer with two rows of flat teeth. Ptery- 

 goid ( ?) with numerous slender conical 



teeth. This group stands in somewhat the 

 same relation to the typical Rhynchoce- 

 phalia as that which the Pythonomorpha 

 bear to the Laeertilia. Evidently derived 

 from primitive land or shore rhynchoce- 

 pbalians, it has taken somewhat the same 

 course in evolution as that followed by the 

 iehthyosaurians and parasuchians. Proia 

 both of these groups it differs very consid- 

 erably in the structure of the vertebree, 

 limbs and skull. It is sharply separated 

 from both by the characters of dentition. 

 The name Thalattosauria has been used to 

 designate this group. 



An Anomaly in the Arterial System of the 

 Dog: John C. Brown. (Introduced by 

 H. F. Nachtrieb.) 



The right subclavian artery arises from 

 the dorsal aorta beyond the origin of the 

 left subclavian artery and passes dorsad to 

 the oesophagus and trachea before reach- 

 ing the right fore limb. The right fourth 

 branchial arch is entirely wanting. 



The Brain and Nerve Cord of Placobdella 

 pediculata: Illustrated by wax models 

 made after the Born method by E. E. 

 Hemingway. (Presented by Professor 

 Henry P. Nachtrieb.) 

 Placobdella pediculata Moore is a new 

 species of leech parasitic in the gill cham- 

 bers of the sheepshead. The description 

 of this leech has not yet been published, but 

 will appear in connection with Mr. Hem- 

 ingway's account of the anatomy of the 

 animal. In general the results of Mr. 

 Hemingway's work confirm the conclusions 

 reached by "Whitman for Clepsine hollensis 

 and other species. The models represented 

 the brain, the ganglion of a typical somite 

 and the posterior mass of ganglia. 



TJie Mechanism of Feeding and Breathing 

 in the Lamprey: Jean Dawson, Univer- 

 sity of Michigan. (Presented by Jacob 

 Reighard.) 



