The Cambridge natural history, Vol. 04 (of 10)Note 216 — Chapter X · ARACHNIDA (CONTINUED)—DELOBRANCHIATA = MEROSTOMATA—XIPHOSURAReading editionA rudimentary ninth pair of ostia are described anteriorly.◇Copy noteReturn to CHAPTER X ARACHNIDA (CONTINUED)—DELOBRANCHIATA = MEROSTOMATA—XIPHOSURA