Since you have great library facilities available, get this book "Invertebrate Paleontology and Evolution" by E.N.K. Clarkson, 4th edition. It is highly readable. It will help you understand about those sponges (BTW, many still have Si spicules).
This is in the Washington DC suburbs. We have Library of Congress available 20 minutes away, but the university libraries here are OK, as are the public libraries.
We probably have that one around here somewhere. Last year I moved out several thousand books that we no longer needed because they were out of date or were on-line.