I50 REPORTS ON INVESTIGATIONS AND PROJECTS. 



and notes were taken, and it is hoped that further collections may be made. 

 Two of these sharks have not yet been identified. 



Numbers of the southern stingray, Dasyatis hastata, were taken, mainly at 

 the Marquesas, but no early embryos were obtained. In this ray, as the 

 writer has found to be the case in its near relative, D. say, the left ovary and 

 left uterus only are functional. 



Several species of bony fishes were collected, measured, weighed, dissected, 

 and peculiarities of structure noted. Notes were also made on the contents 

 of the digestive tract and on the condition of the reproductive organs. 



Studies of Echini of Montego Bay, by Robert Tracy Jackson, Boston Society 



of Natural History. 



Having recently been engaged on a study of recent and fossil echini, I was 

 glad to have the privilege of joining the Carnegie Institution of Washington 

 Expedition to Jamaica in order to extend my studies on certain species oc- 

 curring in that region. 



Centrechinus setosus (Diadema setosum auct.) is vastly abundant at Mon- 

 tego Bay. The adult is characterized by the fact that three oculars reach the 

 periproct, or are insert, namely, i, v, iv, or the bivium and the left ocular of 

 the trivium. While there is considerable variation (principally either i, v, iv, 

 II, or all insert as progressive variants), i, v, iv insert is strongly the species' 

 character. In young specimens up to 14 mm. in diameter all oculars are 

 exsert and genital pores are entirely wanting. With later growth, as a devel- 

 oping feature, gradually oculars begin to travel in, reaching the periproct, and 

 they do so in the sequence v, i, iv, or i, v, iv, the former order prevailing. 

 With growth, perforations also soon appear in each of the genital plates. 

 Centrechinus has a very slow, not a rapid or accelerated development as com- 

 pared with more specialized echini, such as members of the family Echinidae, 

 and Strongylocentrotus drobachiensis. This is in complete accord with 

 what Professor Hyatt has shown in fossil cephalopods, that primitive types 

 with the same degree of growth have a much slower rate of development 

 than specialized types. In young Centrechinus auricles of the perignathic 

 girdle exist as slender separate styles, whereas in the adult these structures 

 are broad and lamellar and arch over the ambulacra, meeting in a median 

 suture. Apophyses also are very slight in the young, whereas in the adult 

 they form quite high ridges. The structure of the teeth and dental capsules 

 were observed in a number of genera. 



Tripneustes esculentus is quite abundant at Montego Bay and attains a 

 large size, but young specimens were infrequent. Of this species, material 

 previously studied* shows a quite wide range of variation as to which oculars 

 reach the periproct, but the variation with few exceptions is very definite. 

 Omitting the exceptions for brevity, in adults ocular i alone may rarely be 

 insert (8 cases seen in 1,133 specimens), or i, v ; or i, v, iv; or i, v, iv, 11 ; and 

 finally all five oculars may be insert. This range was seen in series from a 

 number of localities, but the typical character and the percentages of variants 

 therefrom vary a good deal with different localities. In Tripneustes from 

 Bermuda oculars i, v are insert as the typical local character. In Florida 

 material, oculars i, v are still insert as the character, but with a lower per- 

 centage. In the Bahamas i, v insert occurs, but has passed into the phase 

 of a common arrested variant, and i, v, iv insert is the typical local character. 



* R. T. Jackson. Phylogeny of the Echini. Mem. Boston Soc, Nat. Hist, vol. 7, 1912. 



