ZOOLOGY. 711 



ruptly decurved. The sexes are further distinguishable by the genital 

 openings on the under side of the first pair of abdominal appendages, 

 the exits of the oviducts in the female being transverse slits, while the 

 external genital apparatus of the male consists of two papillae with cir- 

 cular openings at the ends. The claws of the young male are essen- 

 tially like those of the female. Prof. B. F. Koons examined "at least 

 one thousand specimens of exuviae or cast-off" shells along the shores of 

 Long Island Sound, about ISew Haven and Vineyard Sound," and 

 "among all of these not a single specimen with the modified claw was 

 found." A closer examination of the cast shells, however, revealed the 

 other sexual characters and indicated that the males and females were 

 nearly equally numerous. The conclusion, therefore, was that the male 

 assumed the peculiar claws in the last stage of development, and that 

 "it is possible that he never sheds his shell after the modified claw is 

 acquired, because, as stated above, of over one thousand specimens 

 examined, not a single specimen possessing this character was found. 

 Further, we are led to believe that large Limuli rarely, possibly never, 

 shed, because among all those examined there were no large exuviae." 

 {Am. Nat., vol. xvn, pp. 1297-1299.) 



These observations are mainly reiterations of some made many years 

 before by Dr. S. Lockwood (Am. Nat., 1871, p. 257), but that gentleman 

 recorded the finding of large cast shells. 



Number of Cirripeds. — The cirripeds collected by the Challenger 

 Expedition have been studied and reported on by Dr. P. P. C. Hoek, 

 and in connection with the report an interesting historical sketch of 

 the group is given. One hundred and forty-seven species of the sub- 

 class were described by Darwin in his celebrated monographs, and only 

 18 were known to Dr. Hoek by have been added up to the time of his 

 studies. Sixty species previously unknown apparently were discovered 

 among the collections of the Challenger. The number of living spe- 

 cies, exclusive of the suctorial forms, has been thus raised to 225, repre- 

 senting 34 genera. The most noticeable feature of the new additions is 

 the great increase of the genus Scalpellum. Six species were known to 

 Darwin, and 5 were subsequently made known, but Dr. Hoek has recog- 

 nized 43 new species in the Challenger collections, thus enlarging the 

 number to 54. The genus Verruca received the next greatest acces- 

 sions. The number known to Darwin was 4, and 6 new ones were dis- 

 covered by Dr. Hoek, thus increasing the number to 10. According 

 to Dr. Hoek, " the occurrence of Scalpellum and Verruca hi the great 

 depths of the ocean coincides in a striking manner with the paleonto- 

 logical history of these genera." It is noteworthy, however, that " the 

 fossil species of Verruca resemble much more those of the same genus 

 which at present inhabit shallow water than those occurring at a con- 

 siderable depth ; the latter form together a very characteristic division 

 of the genus. With regard to the genus Scalpellum, the fossil tonus 



